Answer:
break the German-Soviet nonaggression pact
Step-by-step explanation:
In 1939, Germany and the Soviet Union agreed to signed the the German-Soviet nonaggression pact. Through this agreement, the two countries agreed that they should not take military action toward one another for the next 10 years.
Germany felt that this pact was necessary for their plan to conquest in Europe because their strongest enemies (Britain and France) were located on the west from Germany. While Soviet union was located on the east from Germany. Germany didn't want to be surrounded from both directions during the war.
Eventually, Germany broke the pact on June 22, 1941 and invaded Soviet Union's territory to strengthen their military position.