Dear Greg
It was rank and file communists who went to Spain to fight the fascists when the liberal democracies of western Europe imposed an arms blockade on the democratically elected republican govt of Spain.
It was the communists in east London who led the working class of that city in the battle to stop the British Union of Fascists at the Battle of Cable St in 1936.A fight which basically stopped the British nazis from growing into a force that could take power in the late 1930s.

It was the Russian Red Army , created by Trotsky, that [in the words of Churchill ] "tore the guts out of the nazi war machine".

Have a listen to the Ballad of Jamie Foyers by Ewan McColl,his homage to the ordinary men from Scotlaand who went to fight in Spain to oppose the spreading threat of fascism.

In the 1930s it seemed that nothing could stop Hitler from taking over the whole of Europe.McColl's generation stood up to be counted and his work is on the side of humanity in all he did .

Read Phil Piratin's book "My Flag Is Red " for an insight into left politics and the Communist Party in Britain in the 1930s and 1940s.
Ifor