Pom-pom or Bofors depends on the air threat

The pom-pom's belt feed suited navies expecting repeated attacks and long defensive engagements, while the Bofors offered greater reach for disrupting or deterring smaller groups sooner. British planning for operations in the Mediterranean and South China Sea differed from American expectations for carrier warfare across the Pacific, shaping each navy's priorities. Both weapons belonged inside a layered defence in which fighters, heavy AA, medium AA, and light AA progressively broke up an incoming strike. Mission and doctrine determine the useful choice between the two 40 mm guns.