It's very well documented that Lenin returned to Russia from exile with the help of Germany, and made significant use of German money and military supplies during the revolution. He even got shit for it from his own communist party. He kept in their good graces by promising to start a communist revolution in Germany next. Funny how that one never quite got off the ground...
And then the Nazis came to power, arrested all the communists, and eventually broke the alliance with the ussr.
The info's pretty easy to find, Google will get you some good articles about it.
Stability doesn't mean "peace" it means "things don't get worse." And I think we both know that things could be A LOT worse.