Why did Germany enter World War 2?

Germany *started* World War II. Their purpose was spelled out very clearly in Hitler's book, "Mein Kampf" (My Struggle). Hitler wanted revenge on France and Britain for Their victory in the first war and he wanted to acquire vast territories in Eastern Europe, exterminate or enslave the people living there, and let Germans live there. Michael Montagne Germany didn't "enter" World War Two, Germany "started" World War Two by invading Poland in September, 1939. A better (historically more accurate) question might be, "Why did Germany start World War Two?"
Germany didn't enter World War 2. They helped it on it's way. Basically, Hitler wanted to break the terms of the Treaty of Versailles and he pushed it too far and conflict was ignited.