 The Nationalists, the Communists and other elements in the Northern Expedition at the time were supported by the Soviet Union, which had already installed puppet governments in nearby Mongolia and Tannu Tuva.From the Japanese perspective, for Manchuria to fall either under Soviet or Nationalist domination was strategically unacceptable, and Zhang Zuolin no longer appeared trustworthy as an ally capable of maintaining a de facto independent Manchuria.Japan needed a context to effectively establish control over Manchuria without combat or foreign intervention, and it believed splitting up the Fengtian clique via replacement of Zhang with a more cooperative leader would do so.