Why did the german invasion of the soviet union succeed at first

Answer: German invasion of the Soviet Union succeeded at first because the Soviets were not prepared.

Explanation:

The Germans invasion of the Soviet Union was successful at first because the Germans prepared and the Soviet Union were not prepared. Before the invasion, the Germans had their troops near the Soviet Union border. Adolf Hitler had move about 3 million German troops and about 690,000 Axis soldiers to the borders of the Soviet Union. Their operations also included several aerial surveillance over Soviet territory some months before the attack.

The Soviet High Command got information about the proposed attack but didn't believe the Germans would attack since the Molotov-Ribbentrop Pact was recently signed and this led to a slow preparation by the Soviet.