On June 22, 1941, the Germans launched Operation Barbarossa: the invasion of the Soviet Union. The invasion was prepared in advance by the SS. Closely following the German army troops were special killing squads called Einsatzgruppen. They would arrive in a town, round up the Jews, and then take them out to be shot.
An eyewitness account from the town of Stanislawow in Eastern Galicia recalled:
We were driven into the cemetery with cruel, brutal beatings. I saw that the Germans were driving the people standing on the one side toward the graves, while those standing on the other were being permitted merely to stand and watch. Then came an order: "Hand over all valuables!" I used the tumult and hubbub, and crossed over to the side of the watchers.
The German stromtroopers, together with the Ukrainian police, took up their stations beside the machine guns. Fifteen of the stormtroops shot, and fifteen others loaded their guns. The Jews leapt naked into the graves. The bullets hit them while jumping. The graves were deep, the naked people fell, one on the other, whether dead or alive. The heap of bodies grew higher and higher. I stood and gazed!
During this period the Germans introduced the first use of gas in killing Jews. They started taking Jews in specially modified trucks where carbon monoxide would flow and kill the Jews.
