In 1939 Adam was appointed an adjutant in the XXIII Army Corps, under the Army Commanders Walther von Reichenau and later in 1941, Friedrich Paulus. On 17 December 1942, he was awarded the Knight's Cross of the Iron Cross. On 31 January 1943, now a colonel, Adam was captured by the Soviet Army after the surrender at Stalingrad, where he was interrogated by Nikolay Dyatlenko. While a prisoner of war, he went to the Central Anti-Fascist School at Krasnogorsk and became a member of the National Committee for a Free Germany. He was also sentenced to death "in absentia" by a Nazi German court.