Complex sentence: However, the designers recommended an increase in the main armament caliber to, a strengthened anti-aircraft battery and reductions in the armor protection, speed, and range, but the start of Operation Barbarossa a month later rendered these plans moot.
Split into simpler sentences: However, the designers recommended an increase in the main armament caliber to, a strengthened anti-aircraft battery and reductions in the armor protection, speed, and range. The opening of Operation Barbarossa a month later rendered these plans moot.