In what country did a civil war in 1946 contribute to tensions between the soviet union and great britain?

Greece and China both had civil wars at this time.

They were both fought before the end of the Second Great war and both were vicious accounting for many deaths. 

I think that the answer you want is Greece. It effectively went on for 10 years -- throughout the 1940s. It was the last hurrah of the British Empire trying to influence countries beyond its borders.