Complex sentence: Himmler brought in 3,000 to 4,000 "Kriegsmarine" (German navy) personnel from Greece to make up the numbers, but this had little effect on the division's fighting ability.
Split into simpler sentences: Himmler brought in 3,000 to 4,000 "Kriegsmarine" (German navy) personnel from Greece to make up the numbers. However, this had little effect on the division's fighting ability.