Which nation did the allies think posed the most serious long term threaten

Most probably the USSR. If you are referring to the Allies during World War 2 then I would say the USSR. During the 1930's there was considerable sympathy and support for Hitler in the West. Many industrialists such as Henry Ford actively supported the Nazis, who were seen as a bastion against communism. It also reflected considerable antisemitism in the West.

d)to gain support for the independence movement.

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