The start of Operation Barbarossa on 22 June 1941 found Colonel Alexiu in command of the 3rd Artillery Regiment from the 10th Artillery Brigade, in charge of two 75mm Gun Battalions and one 100mm Howitzer Battalion. During World War II he fought on the Eastern Front, participating in the Crimean campaign, especially in the July 1942 battle at Eltigen in the Kerch Peninsula. He served as commanding officer of the 4th Artillery Regiment between 1941 and 1942, and in 1942 to 1943 he served as the commanding officer of the artillery 10th division. He was promoted to brigadier general in March 1943, and was put in reserve in June 1943.