Final answer:
The Molotov-Ribbentrop Pact signed between Germany and the USSR in August 1939 was essential to Germany's early success in the war. It neutralized the major eastern threat, the USSR, allowing Germany to focus on subduing the rest of Europe.
Step-by-step explanation:
The pact that was essential to Germany's early success in the war was the Molotov-Ribbentrop Pact signed between Germany and the USSR in August 1939. This pact was crucial for the Nazis as it neutralized the major eastern threat, the USSR, allowing Germany to focus on subduing the rest of Europe. It also secretly included provisions to divide Poland between Germany and the USSR. While Hitler had no intention of honoring the pact in the long term, Soviet Premier Josef Stalin believed that Germany was not strong enough to threaten Soviet territory.