Complex sentence: The two squadrons then began a general engagement with the South Koreans using their 40 and 30 mm guns against the North Korean RPGs, 85 mm, and 35 mm guns.
Split into simpler sentences: The two squadrons then began a general engagement. The South Koreans using their 40 and 30 mm guns against the North Korean RPGs, 85 mm, and 35 mm guns.