On this day, 85 years ago a seismic event in world history took place. At 4am on the 22 June 1941 a massive land force of 3.5 million men, supported by thousands of tanks and aircraft, invaded Soviet territory. Led by Nazi Germany and codenamed ‘Operation Barbarossa’, the significance of the incursion was not lost on contemporaries. ‘We have reached one of the climacterics of the war,’ Prime Minister Winston Churchill told the nation in a radio address delivered that night.

Not for the first time, Churchill would be proved right.

Aided by local collaborators, the Wehrmacht, police auxiliaries, and SS officers, the Einsatzgruppen were charged with executing real and imagined opponents of Nazi Germany

In the immediate weeks and months that followed, it quickly became evident that Operation Barbarossa was more just than a turning point in military terms. As the army brutally forged its path toward Moscow with terrifying speed, four “special action groups” – Einsatzgruppen – totalling around 3,000 men moved at pace into towns and villages behind the front line.

Their task was a simple and bloody one. Aided by local collaborators, the Wehrmacht, police auxiliaries, and SS officers, the Einsatzgruppen were charged with executing real and imagined opponents of Nazi Germany. Initially, they focused principally on communists, partisans, and Jewish men. Soon, however, this was extended to include Jewish women and children too.