Why is Germany so strong?

I was playing as Romanov Poland and gave up Danzig when Germany asked so I could focus on the Soviets when they came knocking, they did, and I was able to relatively easily beat ans annex them, then I turned my gaze west looking to reclaim Danzig and having the full might of Russia under my rule now I figured it'd be pretty easy to roll the Germans but to my surprise they started pushing me. Why was i able to defend against the Soviets and eventually push and annex them but not the germans?