[Tubby Isaacs]

Was there an alliance? I thought they just called themselves Socialists and then arrested the Socialists.

[The Weeping Angel]

Not as such, but the German Communist Party attacked the Social Democrats far more than they did the Nazis, and that did not end well.

[Oboogie]

Was there an alliance? I thought they just called themselves Socialists and then arrested the Socialists.

They did.
I was actually thinking of the Molotov-Ribbentrop Pact, and yes, I'm fully aware that was a non-aggression treaty which is not the same as an alliance, nevertheless it still exemplifies the sheer folly of thinking anything good can come from helping Nazis.