Biden's Bay of Pigs
The Bay of Pigs invasion of Cuba was lost because freedom-loving Cubans were sent into battle with the promise of air support, which our country decided at the last minute not to provide. The result was catastrophic. As a result, decades later we are still trying to pick up the pieces in dealing with Cuba (which we lost as a result of military incompetence). United States air power is the single most important element in our international policy. We just lost another country (Afghanistan) because of withholding such power.
