Complex sentence: In December 1943,56 groups were assigned to the strategic reserve as OTU parent units or RTUs, and the AAF had reached its maximum size, with 269 groups active.
Split into simpler sentences: In December 1943,56 groups were assigned to the strategic reserve as OTU parent units or RTUs. At the end of 1943 the AAF reached its maximum size, with 269 groups active.