We examine how Hitler's rise in Germany created a fear in the Russian High Command and the need for collective security against fascists. 

Key events on helping to spread fear and escalated the purges :

1936 — Spanish Civil War broke out — Soviet Union aided the Republicans against the Nationalists who received Nazi and Italian aid 

• 1936 — Anti-Comintern Pact signed with Italy, Japan and Germany to counter Communist influence 

• 1937 Japan invaded China — Soviet military aid sent to Nationalist Chinese • 1938 — Border clashes between Red Army and Japanese forces in Lake Khasan.