18. Oplans 316 and 312: Invading Cuba in 1962
During the Cuban Missile Crisis, the Joint Chiefs of Staff unanimously agreed that invading Cuba was the only solution. They presented president Kennedy with two options: Oplan 316 for a full invasion, and Oplan 312 for aerial strikes to take out Soviet missiles in Cuba, followed by an invasion if necessary. The hawks, led by Air Force general Curtis LeMay, had a clear preference for the full invasion. Planners expected 18,500 US casualties in the first ten days of the invasion, assuming no nuclear explosions.
Unbeknownst to planners, Soviet forces in Cuba had tactical nukes, and their commander had been preauthorized to use them at his discretion. As the crisis intensified, that discretion was withdrawn, but whether that would have kept Soviet forces on the ground from using them, is debatable. If the Soviets used nukes in Cuba, the US intended an overwhelming nuclear response. Things could easily have escalated from there to a full blown nuclear exchange. Fortunately, Kennedy resisted the pressure from his military, and relying on diplomacy, back channels, and blockade, successfully diffused the crisis without triggering WWIII.