Strategic bombing
During WWII, there was a debate between strategic bombing and tactical bombing. Strategic bombing focused on targets such as factories, railroads, oil refineries, and heavily populated areas such as cities and towns, and required heavy four-engine bombers carrying large payloads of ordnance or a single heavy four-engine bomber carrying a nuclear weapon flying deep into enemy territory. Tactical bombing focused on concentration of combatants, command and control centers, airfields, and ammunition dumps, and required attack aircraft, dive bombers, and fighter bombers that could fly low over the battlefield.