Complex sentence: At that time Italian warships were equipped for the most part with US built naval cannons, with the USN 5-inch (127mm) gun and the Bofors 40mm/L60 being the most numerous.
Split into simpler sentences: At that time Italian warships were equipped for the most part with US built naval cannons. The USN 5-inch (127mm) gun and the Bofors 40mm/L60 being the most numerous.