He assisted the Soviet Union as a prisoner-of-war as one of the leaders of the National Committee for a Free Germany formed mostly of the German prisoners of war in the USSR.

Seydlitz-Kurzbach was born in Hamburg, Germany, into the noble Prussian Seydlitz family [de].

[1] When the entire army was trapped in the city in the course of the Soviet Operation Uranus, Seydlitz was one of the generals who argued most forcefully in favour of a breakout or a surrender, against Hitler’s orders.

[3][4] A few days later, Seydlitz fled the German lines under fire from his own side with a group of other officers.

Seydlitz was a leader in the forming, under Soviet supervision, of an anti-Nazi organisation, the League of German Officers, and was made a member of the National Committee for a Free Germany.

Seydlitz's idea of creating an anti-Nazi force of some 40,000 German prisoners-of-war to be airlifted into Germany was never seriously considered.

He was put on trial for responsibility for actions against Soviet POWs and the civilian population while in Wehrmacht service.