On April 17, 1961, a ragtag bunch of Cuban exiles backed by the U.S. tried to invade Cuba at the Bay of Pigs. The invasion was a mess of poor planning and miserable execution. Most of the 1500 people were killed or captured, and the U.S. government was forced to pay 53 million dollars for the release of the prisoners. Cuban ties with the Soviets were strengthened, and the stage was set for the Cuban Missile Crisis six months later.

In short, things could hardly have gone worse.

Soon after the invasion, President Kennedy asked, “How could I have been so stupid to let them go ahead?” But he hadn’t been alone in the decision—the vote to go ahead had been unanimous among his senior advisers

Officially, that is. It turns out several of them had serious doubts in their own minds, but everybody told the President what they thought he wanted to hear. A really bad idea went unchallenged, and the result was a catastrophe.

During the Missile Crisis later that year, Kennedy made a point of encouraging the collision of ideas among his advisers. They argued and disagreed and hashed out options. The result was a peaceful conclusion of a complex crisis.

The message is clear: if a disaster is what you’re after, surround yourself with “yes” men. They’ll be good company in the lifeboat.

But the business world is different, you say. You can’t run a business unless you are united behind a single vision. That’s absolutely right in one way—and absolutely wrong in another.

Research by Jeffrey Sonnenfeld at Yale shows that boards of directors that punish dissent and stress unity often wind up in bad business patterns, while corporations with highly contentious boards are the most successful. These are the boards where a wide range of viewpoints will be heard, and tough questions asked. All ideas must withstand a withering crossfire of challenge, so the bad ones have a chance of being shot down.

Corporations with boards in which conformity was prized and dissent punished include Tyco, WorldCom, and Enron.

So much for “United We Stand,” right?

Well… not exactly. There’s a limit. Once a decision is made, it’s time to drop the differences and band together in pursuit of that shared vision. A great leader is one who insists on the honest, open collision of ideas during the decision process, then makes it clear that everyone must walk out of the meeting united behind the final decision. Too often, we stress the unity part and forget that a messy, contentious process makes it MORE likely that we’ll be unifying behind a good idea instead of a stinker.

Skip that crossfire, and you might end up standing in smiling unity behind your decision—and wondering, too late, what that tick, tick, ticking sound is.