Complex sentence: The first German garrison unit was the 164th Infantry Division (a.k.a. Fortress Division Crete,), succeeded in 1943-1944 by the 22nd Infantry Division.
Split into simpler sentences: The first German garrison unit was the 164th Infantry Division (a.k.a. Fortress Division Crete,). The 164th was succeeded in 1943-1944 by the 22nd Infantry Division.