What was the main action that sparked the us declaration of the truman doctrine?

It was communism that sparked the Truman doctrine. In 1947 the British Government said they could no longer afford to help Greece and Turkey fight communism both economically or militarily. President Truman believing these countries were in a danger of communism then created the Truman doctrine, which was a promise that the USA would do whatever necessary both economically and militarily to prevent communism from spreading.

explanation:

japan participated in world war i from 1914 to 1918 in an alliance with entente powers and played an important role in securing the sea lanes in the west pacific and indian oceans against the imperial german navy as the member of the allies.

the answer is a new goverment.