Joseph Stalin was the dictator of the Communist USSR
Stalin was concerned about Hitler - who hated and had promised to destroy Communism - but he was also wary of the USA, Britain and France
Relations had started to improve in 1934 when the USSR had finally been allowed to join the League of Nations, and in May 1935 a treaty of mutual assistance was signed with France
Stalin decided that it was worth cooperating with capitalist states if it meant that Hitler's expansion in the East could be stopped