|Original Members from 07/1918||USSR and Japan (under non-aggression treaty)|
|Members from 10/1918||USSR, Japan, Manchukuo, Thailand, Maoist government of China|
Unlike the EA, the Big 5 was an informal alliance with no formal pact, treaty, or rules (although the July 1918 USSR-Japan Treaty can be considered a pact for the alliance). The Big 5 worked only as an alliance of countries. However, Manchukuo, the Japanese puppet state in Manchuria was very closely linked to the Maoist government and the Japanese authorities.
The USSR planned to admit Bulgaria, Romania and the DRA in the alliance after the war. The Japanese did include their puppet-state of Indochina and "New Indonesia" (former Dutch East Indies) as "honorary members".