The Philippine Sea, showing the countries and islands on its borders (Google Earth).
How and when did this area of the Pacific Ocean become the Philippine Sea?
The Philippine Sea is a diamond-shaped area of the North Pacific Ocean (meaning north of the equator) east of the Philippines and south of Japan. It is the largest single sea in the world, almost twice as big as the South China Sea and almost six times bigger than the Sea of Japan.
The Philippine Sea is a marginal sea, bordered by the Philippines and Taiwan on the west, the Okinawa Archipelago (Ryukyu Islands) and the eastern part of Japan up to the vicinity of Tokyo on the north, the north-south ridge formed by the Bonin and Northern Mariana Islands on the east, and Yap Island, Palau and Morotai Island of Indonesia on the south.
This body of water used to be simply called the Pacific Ocean. How and when did the Philippine Sea get its present name?
Philippine Sea on Wikipedia
I was curious about this so I did some investigations, starting with Wikipedia.
Under “History” in its Wikipedia entry, the passage below is written:
The first European to navigate the Philippine Sea was Ferdinand Magellan in 1521, who named it Mar Filipinas when he and his men were in the Mariana Islands prior to the exploration of the Philippines. Later it was discovered by other Spanish explorers from 1522 to 1565.
This is patently false: Magellan could not have named a body of water after a land he have not yet discovered, could he? Not to mention that the name “Felipinas” itself would not be used until Villalobos reached Leyte and Samar in 1543 and named them after Philip II, more than twenty years after Magellan’s demise.
Slightly disgusted that such an obvious falsehood could even be in Wikipedia, I turned to the Tagalog Wikipedia but it was equally unhelpful: its Philippine Sea article is a stub.
Checking on the Japanese Wikipedia, I read the following under “Name (名称)” (translated from the original Japanese):
The name was first used by the US Navy after the Battle of the Philippine Sea (called the Battle of the Mariana Sea by the Japanese) during World War II.
After the war, in 1952, the IHB defined the boundaries of the Philippine Sea, and the name is now used around the world.
On the other hand, Japan temporarily withdrew from the IHB after the war, but rejoined in 1952, so the Japanese government officially recognizes the name Philippine Sea. However, the name has not been widely used in Japan, and is not used on official nautical charts issued by the Japan Coast Guard.
However, in Japan, which is a country prone to earthquakes, the name Philippine Sea Plate is frequently used as the name of the plate related to the occurrence of plate boundary earthquakes, mainly in the context of disaster prevention measures.
Now this article is substantially more helpful than the other two and is something we can actually check by surveying old maps.
Philippine Sea in old maps
A cursory look at the “Mother of Philippine maps” published in 1734 in Manila–the Carta hydrographica y chorographica de las Yslas Filipinas–at the Library of Congress reveals that the Jesuit cartographer Velarde did not bother to name the sea east of the Philippines, not even with “Pacific Ocean”.
Subsequent maps either use “Pacific Ocean” or leave this blank.
One exception, a map published by Antonio Zatta in Venice in 1785 based on the Velarde map, named this sea “Mar del Sud” (South Sea). Mar del Sud is explorer Vasco Núñez de Balboa’s appellation for the Pacific Ocean which he sighted in 1513 after crossing the Isthmus of Panama.
In the early 1900s, when the Philippines was firmly in US control, Philippine maps still mention no “Philippine Sea.”
1908 map of the Philippine Islands, published by the World Book Company in New York, showing Pacific Ocean (Library of Congress)
As late as 1945 during the height of the Pacific War, the CIA (then part of the US military called the Office of Strategic Services) was still using a map–recently declassified–of the Philippines which labeled the Philippine Sea the North Pacific Ocean.
Approaches to Japan, March 1945 (CIA)
On the other hand, another map prepared by the US Army in 1944 not intended for sale or distribution indicates the Philippine Sea for the first time.
Philippine Islands map prepared by the US Army 1944
It is not clear which particular map started the naming of Philippine Sea, but immediately before or during the Pacific War, the US military started using maps with the Philippine Sea label, no doubt anticipating its importance in the coming naval battles with Japan.
Some of the biggest and fiercest battles during the Pacific War between US and Japanese forces were fought in and around the Philippine Sea:
- 1944 June Battle of Philippine Sea (called Naval Battle off Marianas in Japanese)
- 1944 June-July Battle of Saipan
- 1944 October Battle of Leyte Gulf (originally called Naval Battle off the Philippines in Japanese)
- 1945 February-March Battle of Iwo Jima
- 1945 April-June Battle of Okinawa
The following two maps come from the archives of General MacArthur, supreme commander of the Allied forces in the Pacific and effective ruler of occupied Japan after the war.
It is unclear whether the map directly below was made by the Japanese or the US, or whether it was made before the Japanese invasion of the Philippines or after the Pacific War has been concluded, but the Philippine Sea label is there along with its Japanese wording 比島海 (Hitōkai lit. Philippine Islands Sea).
Invasion of Philippines Complete, General Douglas MacArthur Report Maps, 1942–1947 (US National Archives)
It is purportedly a map of the Japanese invasion of the Philippines after the attack on Pearl Harbor, with place names in Japanese. But the fonts and colors used in the maps above and below are very similar, so it is possible that both were prepared by the US (with Japanese input in case of the first map).
The 1945 bombing operations map below also labels the sea between Okinawa and the Iwo Jima in the Bonin Islands the Philippine Sea, indicating that the appellation does not only apply to the immediate vicinity of the Philippines. It is clearly separated from the Pacific Ocean by the Bonin Islands-Marianas ridge.
Japan Bombing Operations Complete Map, General Douglas MacArthur Report Maps, 1942–1947 (US National Archives)
Looking at these maps, it looks more likely that the Battle of the Philippine Sea was named after the sea that the Americans have earlier identified in their maps, rather than the other way around, as the Japanese Wikipedia says.
Finally, a few months after the Philippines was liberated from Japanese control in 1945, National Geographic magazine published a map of the country with the Philippine Sea label.
Philippines map by National Geographic 1945
As per National Geographic:
The Philippines were liberated from the Japanese by MacArthur’s forces just months before this map was published in March 1945. This map, which accompanied the article “What Luzon Means to Uncle Sam,” features the provinces and their capitals as well as airfields.
As we have read above, it would be another 7 years, at the 1952 International Hydrographic Conference, when the name Philippine Sea would be formally adopted internationally.
Naming of the Philippine Sea
Sleuthing around the internet, I found it odd that I couldn’t find any substantial article about the Philippine Sea from Philippine sources (except for a few about the recently discovered Apolaki Caldera in Benham Rise). It’s as if nobody is interested enough to write about the largest sea in the world that is named after their country.
Fortunately, after searching from Japanese sources, I finally discovered the only article about the history of the naming of the Philippine sea that I have found enlightening. It was written by Hiroshi Nakajima, Executive Director of the Pacific Studies Association, published in the defunct Yashinomi Daigaku (Coconut University).
I have reproduced the entire article below, translated from the original Japanese:
Where is the northern end of the Philippine Sea?
Most people probably think that Saipan is a paradise floating on the Pacific Ocean. However, while its east coast is in the Pacific Ocean, its west coast faces the Philippine Sea. Most people probably don’t even suspect that the entire eastern coast of the Japanese archipelago is not in the Pacific Ocean. However, most of what we think are the Pacific Ocean sides of Kyushu, Shikoku, Kinki, and Chubu actually face the Philippine Sea. Why are we unaware of this well-established international rule?
Looking at the map on page 2 of this magazine, or at the map distributed free of charge by the Marianas Visitors Bureau, we can see that sea to the west of Saipan is the Philippine Sea.
Most Japanese people think that Saipan is in the Pacific Ocean, so when they come to Saipan and look at a map and see that the Pacific Ocean ends on the east coast of Saipan and the Philippine Sea is to the west, they may think it is strange, but at least in terms of international hydrography, Saipan is located at the western end of the North Pacific Ocean (the Pacific Ocean north of the equator).
Who decided this and when? It was decided at the International Hydrographic Conference held in 1952 by the International Hydrographic Bureau, an international organization to which Japan is a member. This decision was revised in part at the 11th International Hydrographic Conference in 1997, but the basics remain unchanged.
If the sea to the west of Saipan is the Philippine Sea, how wide is that sea? Given the name Philippine Sea, it is easy to imagine that the sea is connected all the way to the Philippines in the west.
But where is the northern end of the Philippine Sea? Is it around Farallon de Pajaros Island, the northern tip of the Mariana Islands? Or is it even further north, around the Ogasawara Islands? Surprisingly, the northern end of the Philippine Sea is the southern tip of the Izu Peninsula.
According to the boundaries of the Philippine Sea determined at the International Hydrographic Conference in 1952, the northern end of the eastern side is at 34°39′N and 138°58′50″E, which is around the southeastern tip of Shimoda City, Shizuoka Prefecture.
The eastern edge of the Philippine Sea runs from there through the Izu Islands at 33°N and 139°50′E, down south to the Ogasawara Islands, the Mariana Islands, Yap Island, Babeldaob Island in Palau, and finally to the northern tip of Morotai Island in the Philippines.
The waves of the Philippine Sea wash the shores of Japan
The western side of the Philippine Sea runs from the northern tip of Morotai Island, north along the eastern coast of the Philippine Islands, through Taiwan and the Ryukyu Islands, and reaches the southern tip of the Osumi Peninsula in Kagoshima Prefecture (31°16′40″N, 131°08′E).
And that’s not all. It also runs north along the eastern coast of Kyushu, reaches Sekizaki (Jizosaki) in Kita Amabe District, Oita Prefecture, crosses Hayasui Seto (Hoyo Strait), and reaches Sadamisaki in Nishiuwa District, Ehime Prefecture, in Shikoku, so this area is the actual northern end of the western edge.
The sea that faces Honshu, Shikoku, and Kyushu from Shimoda City, Shizuoka Prefecture to the southern tip of the Osumi Peninsula in Kagoshima Prefecture is the Philippine Sea.
However, people living in these regions do not know that the sea in front of them is the Philippine Sea under international agreements. It is not taught in schools, and there is no such marking on Japanese maps.
Decided during Japan’s withdrawal
The reason this happened was because the views of those involved in international hydrography about the North Pacific changed before and after World War II, and Japan had withdrawn from the International Hydrographic Bureau from 1940 to 1950, sandwiching the Greater East Asian War (Pacific War), so in a sense it was left out of the loop.
In 1949, four years after Japan’s defeat, a letter was received from Admiral Nares, Executive Director of the International Hydrographic Bureau. The letter stated that the International Hydrographic Bureau would be making new proposals regarding the boundaries and names of oceans, and that the Japanese Hydrographic Bureau was asked to respond if they had any opinions on the matter.
One of the new proposals was to give the name Philippine Sea to the ocean that had previously been considered part of the North Pacific (the Pacific Ocean north of the equator). The ocean in question was exactly the area mentioned above.
After numerous discussions with the Japan Coast Guard and, since Japan was under occupation, also listening to the opinions of officials at the Supreme Commander for the Allied Powers, the Hydrographic Department responded that if the sea that had been considered part of the North Pacific were to become the Philippine Sea, it would mean that not only would nautical charts and sailing directions be required to be revised, but also all textbooks and geography books, which would be extremely expensive, and that the name should not be used, and that the sea should remain part of the North Pacific as before.
Also, since this issue is closely related to geophysical research, the Geophysical Research Liaison Committee of the Science Council of Japan sent a questionnaire in the name of its chairman to over 70 members, requesting their responses, and held an extraordinary special committee meeting to deliberate the responses, reaching the following conclusion:
It should remain part of the North Pacific as before. If it is to be separated from the North Pacific, the border should be the 20th parallel north, and the area north of that will be the Ogasawara Sea, and the area south of that will be the Philippine Sea.
If it is unavoidable to separate it from the North Pacific, and it cannot be divided into two, north and south, it should be called the Mariana Sea.
This conclusion was then communicated to the International Hydrographic Bureau via the US Navy in the Far East as a reference proposal from the Science Council of Japan.
However, neither the Hydrographic Bureau’s requests nor the reference proposal from the Science Council of Japan were taken up, and the International Hydrographic Conference in 1952 decided on Philippine Sea as originally proposed, and the following year, in 1953, the International Hydrographic Bureau published the third edition of Special Publication 23, “Limits of Oceans and Seas,” in which it explicitly stated the name Philippine Sea.
How did Japanese officials respond to this? To this day, the Hydrographic Bureau has consistently refrained from using the name Philippine Sea on the nautical charts it produces, and geophysicists and geographers have also opposed map companies and others using the name Philippine Sea based on the International Hydrographic Bureau’s “Limits of Oceans and Seas.”
As a result, the Philippine Sea is not taught in school education in Japan, and people only become aware of its existence when they look at maps from overseas. And even if you look up the term Philippine Sea in an encyclopedia, it only has a very vague definition, such as “the sea area in the western Pacific Ocean, stretching along the eastern edge of the Philippine Islands” (Encyclopedia Britannica).
The Philippine Sea will remain
The reason why the International Hydrographic Bureau (now renamed the International Hydrographic Organization) originally created the Philippine Sea was because it has the Philippine Basin on its bottom, which is separated from the North Pacific Basin by a volcanic shallow bank and has unique oceanographic conditions, and it has the Philippine Trench, one of the world’s deepest. In addition, it is separated from the North Pacific by the Izu-Ogasawara Ridge and the Mariana Ridge, so it matches the concept of a marginal sea and also the concept of an attached sea in terms of ocean currents, and is therefore scientifically sound.
A marginal sea is a sea that is adjacent to an ocean and connected on the surface, but is separated by a ridge, and an attached sea is a sea that, unlike an ocean, has a small area, does not have its own currents or tides, and is influenced by the ocean to which it belongs.
Incidentally, the International Hydrographic Organization held the 11th International Hydrographic Conference in April 1977, and based on the decision made at that conference, began work the following year in 1978 on the fourth edition of “The Limits of Oceans and Seas.” However, various requests continued to be made by member countries regarding the names of oceans, and in 1986 the fourth draft of the fourth edition was published, which has continued to be used to this day. However, even in this fourth draft, the name Philippine Sea is the same as in the third edition published in 1953.
As mentioned above, the name Philippine Sea is consistent with the concepts of marginal seas and adjoining seas, so it is likely to remain the same in the future.
The reason why the International Hydrographic Organization holds international conferences and publishes “The Limits of Oceans and Seas” is to facilitate the production of nautical charts by countries around the world, and there is no political intention behind it. However, since “The Limits of Oceans and Seas” published by the International Hydrographic Organization is the only authority on international water geography and hydrography, it is only natural that some countries are concerned about the names of oceans.
For example, the Sea of Japan is one of the seas attached to the North Pacific Ocean, but at the United Nations Conference on Geographical Names held in August 1992, representatives from South Korea and the Democratic People’s Republic of Korea raised objections to the name “Sea of Japan” and demanded a readjustment of the ocean’s names (Yomiuri Shimbun).
Furthermore, in 1994, the South Korean government held a meeting of relevant departments and demanded that if the term “Sea of Japan” was used at international conferences, the name “East Sea” used in South Korea be used as well, or that a neutral name such as latitude and longitude be used, and decided not to participate in conferences if this was not accepted (Mainichi Shimbun).
Furthermore, at the First Intergovernmental Meeting on the Northwest Pacific Regional Seas Programme held in September 1994 under the auspices of the United Nations and attended by Japan, South Korea, China and Russia, the English draft practical plan contained the expression “Sea of Japan,” so South Korea insisted on “East Sea.” In the end, they settled on describing the sea area between 121 degrees and 143 degrees east longitude and 33 degrees and 52 degrees north latitude.
If the name “Sea of Japan” is changed to “East Sea” internationally, what will happen to Japan’s Tokai region?
According to Nakajima, Japan proposed to the IHB that the name Pacific Ocean (or North Pacific Ocean) should stay as it was, and submitted alternative naming suggestions if changing the name was unavoidable.
If it has to be separated from the North Pacific, the area south of the 20th parallel north (the latitude just below Okinotori Island) should be named Philippine Sea and the area north the Ogasawara Sea. (Ogasawara Islands are the Japanese-administered Bonin Islands).
Naming proposed by Japan, Philippine Sea south of 20th parallel (just below Okinotori Island), and Ogasawara Sea to the north.
The Japanese proposed further that if it cannot be divided into two, then it should be named Mariana Sea. As noted above, what the US refers to as the Battle of Philippine Sea is known in Japanese as the Naval Battle off Marianas.
Naming proposed by Japan: instead of Philippine Sea, the area should be called Mariana Sea.
The International Hydrographic Bureau, however, did not take up these proposals and went on with the original idea of naming this area the Philippine Sea.
Frankly though, it is probably unsuitable to name this huge part of the Pacific after an archipelago 1/300th the size of the Philippines, nor to divide it into north and south without any geographical features to separate the two parts other than an imaginary horizontal line 20° north of the equator.
Philippine Sea according to the Japanese
As we have seen above, although Japan officially recognizes the name Philippine Sea for this body of water, it also does not actively teach it in its schools. For the ordinary Japanese, the sea west of Japan is the Sea of Japan, and that on the east is just the Pacific Ocean.
And so it continued for more than 60 years, until the advent of the Internet and mapping apps in smart phones.
It’s not surprising then that many Japanese are confused when they open a mapping app and find “Philippine Sea” there instead of the usual “Pacific Ocean.”
Here’s a humorous blog post about two men working and looking at a weather app in Kochi Prefecture facing the Philippine Sea (フィリピン海) without them knowing the fact:
Philippine Sea
“Isn’t that the Pacific Ocean?”
“No, not there, this double circle is our current location.”
“Yeah, I know that, but it says Philippine Sea here.”
“Oh, you’re right.”
We looked and sure enough, “Philippine Sea” was written in large letters south of Cape Muroto.
Yugo confirmed it and said again.
“That’s the Pacific Ocean not the Philippine Sea, right?”
“Yeah, it’s the Pacific Ocean alright. Why does it say Philippine Sea?”
“Which country made this app?!”
“Probably the Philippines.”
He laughed loudly and the situation calmed down, but I was so curious that I decided to look it up right away.
The International Hydrographic Organization (IHO)'s 1953 publication, “Limits of Oceans and Seas (Third Edition),” seems to define it this way:
Philippine Sea
A sea area in the North Pacific Ocean off the east coast of the Philippine Islands. The boundaries are:
On the west, the eastern edge of the East Indian Archipelago (notes: Sulu Sea, Celebes Sea, and Molucca Sea), and the eastern boundary of the South China Sea and the East China Sea.
On the north, the southeast coast of Kyushu, the southern edge (note: Shikoku) and eastern edge (note: Awaji Island) of the Seto Inland Sea, and the southern coast of Honshu.
On the east, the ridge that connects Japan with the Ogasawara Islands, the Volcano Islands, and the Mariana Islands. All of these are included in the Philippine Sea.
On the south, a line connecting Guam, Yap, the Palau Islands, and Halmahera.
So that means the whole sea south of Western Japan west of the Izu Peninsula and east of the Nansei Islands is the Philippine Sea.
I stopped Yugo as he was about to leave for the construction site and told him everything I had just learned.
“Huh? We never learned that in social studies!”
“That’s the first time I’ve heard that either.”
So that means…
We both looked at each other.
“When you go fishing at the sea…”
“‘Let’s go to the Philippine Sea.’”
“Oh, that Philippine Sea?”
“Yes, I’m off then, to the Philippine Sea.”
We looked at each other again and laughed, and that was the end.
But still…
Even though I’ve lived to be seventy years old if I round it up, there’s still so much I don’t know. I’m a 65-year-3-month old civil engineer, and I’m ashamed of my ignorance.
Another blogger wonders why it is not taught in schools in Japan.
Philippine Sea
Do you know about the Philippine Sea? You may be familiar with the term Philippine Sea Plate in connection with earthquakes, but you may not have heard much about the Philippine Sea.
So, which sea is the Philippine Sea? The area that people from Kansai assume to be the Pacific Ocean is actually the Philippine Sea. The Philippine Sea is the sea that is surrounded by Japan, Taiwan, the Philippines, and Micronesia.
By the way, if you look at a map of the area around Nagoya Port on Google Maps, you will see the words “Philippine Sea.”
However, the name Philippine Sea has not caught on at all in Japan. It is not taught in schools, so it has not caught on, and I would like to ask why it is not taught. I wonder if it is not acceptable that the name of the country, Philippines, is included. It is easy to understand for the national sentiment, and when you are told that the Kiso River flows into the Philippine Sea, you are left feeling confused.
When Apple first rolled out its mapping app a decade ago to everyone’s ridicule because of its many flaws, Japanese netizens pointed to the inclusion of Philippine Sea near the Japanese coast instead of the usual names they were familiar with.
A blog post by 非天マザー by B-CHAN:
Philippine Sea
Well, this is a trivial thing but it’s now all the rage to play spot the difference games on Apple’s new map app, and here’s a news story in that vein.
Apple to improve new map due to inaccuracies
In this NHK article, it says, “Suruga Bay is also listed as the Philippine Sea.”
If you actually look at Apple’s map, you’ll see this. It shows the Philippine Sea.
This is the Suruga Bay coast of Shizuoka Prefecture.
You might think for a moment, “What the hell is this Philippine Sea? Write it Suruga Bay or the Pacific Ocean!”
But actually, this “Philippine Sea” is correct.
The vast Pacific Ocean is divided into several sections, and the seas near Japan are called the Philippine Sea.
Philippine Sea - Wikipedia
Suruga Bay - Wikipedia
Wowww, I learned something today.
So, Apple’s map isn’t wrong here.
However, it seems strange to see “Philippine Sea” written instead of “Pacific Ocean” and “Suruga Bay” on general Japanese maps, so it would be better to correct the description here at human discretion.
Even if the data is correct, each region has its own unique way of describing it. This is one of the difficult aspects of mapmaking.
Philippine Sea on X
More often than not, the Japanese post about the Philippine Sea on X to express confusion when discovering Philippine Sea so close to the Japanese mainland on mapping apps.
One X user was asking why there was a Philippine Sea showing on his seat-back flight display:
It’s Japan’s 
territorial waters so why Philippine Sea? What’s happening here?
I found this on the in-flight announcement on my airplane 
. A little to the right of the map are Chichijima and Hahajima. To the left is Amami Oshima.
I think there will be government officials on this flight , so I hope to hear a rebuttal soon.
A number of iPhone users were surprised and some other expressed slight annoyance to see the label Philippine Sea (フィリピン海) so close to the Japanese mainland, like this resident (presumably) of Chubu Region near Nagoya, who tweeted:
The attached image is Apple’s mapping app “Maps.” The area of the Philippine Sea is too large no matter how you look at it.
Another X post:
Wh-? Whaat?
Isn’t this the Pacific Ocean?
I googled it and found out that the sea south of Western Japan (west of the Izu Peninsula) is not the Pacific Ocean but the Philippine Sea lol
#太平洋と習ったんだけど
#日向灘
#フィリピン海
I didn’t know that 
Some Japanese–more knowledgeable than others–actually advocate adopting the Philippine Sea label, to separate the southern (Philippine Sea side) and northern (Pacific Ocean side) part of the eastern side of Japan.
X user 地理ねこ (Geography Cat) tweeted:
One of the reasons why I say that we should recognize the “Philippine Sea side” as well as the “Japan Sea side” is this: the annual precipitation on the “Philippine Sea side” is clearly different from that on the “Pacific Ocean side,” and this is due to the significantly higher amount of precipitation in the summer due to the rainy season and typhoons.
(Image: Japan Meteorological Agency’s Mesh Average Value Map 2020 from https://data.jma.go.jp/obd/stats/etrn/view/atlas.html)
Philippine Sea, going forward
Despite its name, the Philippine Sea is arguably more important to Japan than to the Philippines, which is understandably more preoccupied with the “other” Philippine Sea (the recently christened West Philippine Sea in the South China Sea, site of several ongoing naval clashes with China).
There are several reasons for this.
First, Japan’s largest population centers face the Philippine Sea/North Pacific Ocean and maritime traffic from its five biggest ports (Tokyo, Yokohama, Nagoya, Osaka and Kobe) passes through this area.
Japan maritime routes (Japan Maritime Public Relations Center)
In contrast, Manila, the Philippine capital, faces west towards the Asian mainland, not the Philippine Sea.
Second, Japan lies in one of the most seismically active areas on the planet and the Philippine Sea Plate continuously bumping into the Eurasian Plate causes many earthquakes in the country.
Especially with the recent talk about the mega-earthquake in the Nankai Trough where the two tectonic plates meet just south of the Japanese mainland, almost everybody in Japan has heard about the Philippine Sea Plate that is constantly mentioned in the news.
A century has passed since the Great Kanto Earthquake, and a similar catastrophe would most likely be caused by the same Philippine Sea Plate grinding against the Eurasian Plate.
Philippine Sea Plate (purple), Eurasian Plate (brown) and Okhotsk Plate (green) meet just under Mount Fuji in the vicinity of Tokyo. Izu Peninsula (伊豆半島) indicated with a line is the northern tip of the Philippine Sea. (Izu Peninsula Geopark)
Finally, the Philippine Sea will feature prominently in any future conflict between China and US-Japan-Philippines, especially relating to Taiwan, the other big country bordering the sea.
An organization that is helping popularize the use of Philippine Sea in Japan is the US Naval Forces (which was the original advocate of naming this body of water the Philippine Sea in the first place) which regularly posts about its activities in the waters off Japan, like this tweet, and this, and this:
それでは今日はこのあたりで失礼します。写真はフィリピン海を航行する空母ニミッツ。ではまた！See ya!
(Well, that’s all for today. The photo shows USS Nimitz sailing through the Philippine Sea. See you next time!)
#USSRonaldReagan conducts night flight operations during #ValiantShield24, enhancing proficiency of the #USINDOPACOM #JointForce to deliver multi-axis, multi-domain effects that deter aggression in the #FreeAndOpenIndoPacific.
Conducting live fire training 
#USJohnSMcCain (DDG 56) launched a Standard Missile (SM)2 during training in the Philippine Sea.
@US7thFleet #forcetobereckonedwith
In 2022, the Taiwan visit of US Speaker Nancy Pelosi and the subsequent military exercises conducted around the island by the Chinese Navy were big news in Japan, with the US Navy deploying aircraft carriers–as they normally do–in the waters off Japan (the Philippine Sea).
During this time, one tweet explaining the true size of the Philippine Sea by a Japanese map buff gathered 30K likes, 13K reposts and more than 200 responses ranging from “I didn’t know that!” to “Philippine Sea Plate = Philippine Sea, makes sense” to “That’s an eye-opener” to “All the while I’ve been fishing in the Philippine Sea”.
While watching the news about this Taiwan visit issue, I thought it’s possible that most Japanese people don’t understand what the US military is talking about when they say “Philippine Sea”. About half of the ocean that Japanese people think of as the “Pacific Ocean” is actually the Philippine Sea according to the international definition. Just saying.
Philippine Sea timeline
I got the idea of writing this post because I was curious about how the Philippine Sea got its name and because there was a dearth of useful information (not to mention serious errors) about the subject on the Internet.
Now I know:
The Philippine Sea was first named in the maps produced by the US military during World War II and was formally adopted at the International Hydrographic Conference in 1952.
The boundaries of the Philippine Sea were further specified in the 1953 International Hydrogaphic Bureau publication “Limits of Oceans and Seas.”
Here is a brief timeline:
- 1520 November - Magellan sets eyes on the Pacific Ocean, names it Mar Pacifico
- 1543 - Villalobos names the islands of Leyte and Samar Felipinas
- 1898 December - Spain cedes the Philippine Islands to US
- 1921 June - International Hydrographic Bureau (IHB) is formed; Japan joins as founding member
- 1922 June - US joins IHB
- 1940 January - Japan withdraws from IHB
- 1941 December - Pacific War starts
- 1944 - US Army classified map “Philippine Islands” for use by War and Navy Department labels Philippine Sea
- 1944 June - Battle of Philippine Sea between US and Japanese forces near the Mariana Islands
- 1945 March - National Geographic Magazine publishes “The Philippines” map indicating the Philippine Sea
- 1945 August - Pacific War ends
- 1946 July - Philippines becomes independent from US
- 1949 - Japan Hydrographic Bureau receives letter from IHB requesting opinion about designation of Philippine Sea
- 1950 January - Japan rejoins IHB
- 1952 April - Philippine Sea is adopted at the International Hydrographic Conference, despite Japan’s proposal for other names
- 1953 - IHB publication “Limits of Oceans and Seas” defines the boundaries of the Philippine Sea
- 1955 September Philippines joins IHB
As we can see from the timeline above, the Philippines, devastated during the Pacific War, had virtually no input in naming the Philippine Sea, only joining IHB in 1955 when the Philippine Sea has already been adopted internationally.
(It’s also worth noting that Japan, similarly, had virtually no influence in naming the Sea of Japan, which was adopted by European mapmakers when Japan was in more than 200 years of self-imposed isolation.)
Finally, I end this unexpectedly lengthy post by quoting a tweet from D柵, a resident of Kagawa Prefecture, with the hashtag フィリピン海 (Philippine Sea).
He was probably looking in the direction of the Philippines when he took this photo of a very serene Philippine Sea while standing on the shore in Tokushima Prefecture in the island of Shikoku.
Sea of Tokushima
#フィリピン海
#タイムラインを海にしよう
