On April 16, 1961, the Bay of Pigs was a lonely stretch of water and beach on the southern coast of Cuba. A day later, it was where American sea and air forces landed some 1,400 armed Cuban exiles, as part of President John Kennedy's effort to overthrow dictator Fidel Castro.

Forty-eight hours after that, Kennedy left them stranded on the beach to die or surrender as the invasion collapsed--leaving Cuba to plunge into 50 years of totalitarian darkness.

Half a century later, the Bay of Pigs is still the mother of all American military and foreign-policy disasters. It marks the start of America's bizarre habit of fighting our enemies with one arm pinned firmly behind our back, and dumping our friends when the going gets dicey. It also offers some pungent lessons for our current messes in Libya and Afghanistan.

The plan that April was bold if not exactly straightforward. A CIA-trained army of Cuban exiles was supposed to trigger a popular uprising against Castro's still-shaky regime by landing on Cuban territory and declaring a revolt. The Cubans were told our planes and ships would be on hand to provide any necessary support when they hit the beach on April 17. The CIA and Air Force led the way with prior airstrikes. The aircraft carrier USS Essex and American destroyers circled the Bay of Pigs to cover the landings.

When the exiles ran into tougher-than-expected resistance, however, Kennedy panicked and pulled the plug on the operation, leaving the stranded exiles to their fate. More than 100 were killed, as were four Americans. A triumphant Castro executed hundreds of other resisters, and threw at least 100,000 would-be political opponents in prison.

The long dark night of Communist Cuba had begun.

Before the operation JFK had told his brother Bobby, "I'd rather be an aggressor than a bum." He ended up being both.

And if Kennedy thought abandoning our Cuban allies would save him inconvenience, he was dead wrong. The bungled invasion cemented Castro's ties to the USSR, setting the stage for the nuclear confrontation over missiles on the island the next year--a crisis fueled by Soviet Premier Nikita Khrushchev's belief that the president who panicked at the Bay of Pigs could be bluffed and rolled.

As for JFK, he was determined not to look weak again. He told his National Security Council advisers he wanted them to find another place where he could safely stand firm against Communism. The place they chose was Vietnam.

Yet the real lessons of the Bay of Pigs were and are clear.

First, it revealed the folly of halfway measures when it comes to using American military force. Time and again, presidents convince themselves otherwise--starting with JFK's successor, Lyndon Johnson, in Vietnam.

Striking at an opponent without intending to annihilate his ability to resist (by either conventional or unconventional means) is like waterskiing without skiis. What seems a way to save trouble and expense and keep our options open, is a formula for getting in over our heads, whether we're talking Cuba and Vietnam or Afghanistan and Libya.

The Bay of Pigs also revealed the folly of allowing international opinion to dictate our strategic choices, including our allies in far-off lands. For the sake of not appearing imperialist, Kennedy betrayed the Cubans we'd recruited, as well as their cause. It's a pattern we've doomed ourselves to repeat ever since. Just ask the Vietnamese and Cambodian refugees who wound up on our shores, or Egypt's Hosni Mubarak.

Now the Saudis and Israelis are wondering if they're going to be the next ones left stranded on the beach. So are those Libyan rebels--not to mention President Hamid Karzai of Afghanistan.

The truth behind Henry Kissinger's famous quip that it can be dangerous to be America's enemy but being our friend is fatal, begins with the Bay of Pigs.

Then and later, JFK apologists would blame the whole fiasco on his predecessor, Dwight Eisenhower, who authorized the operation, and on the CIA, who planned and executed it. But the real failure was a president unwilling to commit the full weight of American power to a war undertaken at his behest, for fear it would make him look bad in the eyes of the world.

That's a formula for disaster--as several commanders-in-chief since Kennedy have found. The search for some substitute for victory leads only to defeat--and no memorial is big enough for those we leave behind.

Arthur Herman is a visiting scholar at AEI.

Robert Knudsen, White House