After the war, he joined the police force where he remained for several years until he rejoined the German Army in 1935 as an engineer.

[1] With the rank of Oberstleutnant (lieutenant colonel), he commanded the 51st Engineer Battalion which fought in the Battle of Poland in 1939 and assisted in the capture of Fort Eben-Emael in Belgium on 11 May 1940.

[3] Promoted to Oberst (colonel) in 1942,[1] Mikosch was commander of the 677th Pioneer Regiment, which took part in the Battle of Stalingrad and saw him awarded the Knight's Cross of the Iron Cross with Oak Leaves,[4] and the following year, was temporary commander of the 10th Panzergrenadier Division from late July to late December, during which it fought in Operation Citadel and the Battle of Kiev.

[1] On its return to the front, the 13th Panzer Division took part in the Battle of the Korsun–Cherkassy Pocket and the subsequent retreat to the Bug River.

Having been promoted to Generalleutnant (equivalent to the rank of major general in the United States Army) the previous month, he surrendered to the Soviet forces on 8 April 1945.