Airmobile troops, delivered by helicopter, are practically synonymous with the counterinsurgency in Vietnam — but they were originally meant for tactical nuclear warfare:
Army leaders soon reached the conclusion that ground units would have to be highly dispersed to survive a nuclear attack while simultaneously retaining the ability to mass quickly to exploit an atomic strike on opposing forces. Helicopters would provide the mobility that friendly ground troops needed to capitalize on the ensuing shock and disruption of the enemy, without relying on roads and bridges that probably would be damaged in the exchange.
[...]
In 1957 Howze had prepared a briefing, making a case for what
he termed air cavalry units. The presentation revolved around a tactical scenario, set in Bavaria, between a reinforced air cavalry brigade and an attacking Soviet armored force. Because the American unit needed neither bridges nor roads, friendly engineers and artillery demolished these avenues of approach. Rather than conduct a conventional linear defense, the brigade used observation aircraft to identify targets for Air Force tactical aircraft, employ transport helicopters to land artillery observers behind enemy lines, attack armored columns with helicopter-launched antitank missiles, and engage the foe in depth with helicopter-borne infantry tank-killer teams.