Soon after the outbreak of the Korean War, Japanese Prime Minister Yoshita set it as a government policy to make positive cooperation with the U.S. in its military actions.

Accordingly, the whole territory of Japan was turned into a launching and supply base for U.S. forces in the war, with all its ports used for U.S. warships.

As of January 1953, there were 220 U.S. barracks, 44 airports, 30 harbors, 79 training grounds and 116 communications facilities in Japan, 733 in all.

Most of warplanes and warships, mobilized in the Korean War, were based in Japan.

The Japanese newspaper Akahata on June 25, 1970 said during the war Japan supplied U.S. forces with weaponry, medical materials and food, worth 2.3-2.4 billion U.S. dollars.

On the U.S. order, Japan dispatched servicepersons from the "Imperial Japanese Army" to the war under the name of "volunteers".

They served as "advisers" and "military experts" in the U.S. army, or directly took part in battles.

Reuters was quoted as saying on July 27, 1950 that about 25 000 Japanese troops participated in the war.

Mine-sweeping in the Korean territorial waters was entirely tasked to Japanese.

For example, Japan played a key role in U.S. troops' landing on Inchon, ranging from preparations of the operational plan, shipment of U.S. troops and munitions to mine sweeping.

It handed over to the U.S. army the data on germ weapons, developed in the period of the 2nd World War by the Unit 731 under the "Imperial Japanese Army", and helped it to use them in the war.

Thus, Japan's participation in the war rendered the situation of the war worse.