Here is my entry for the Lessons of the Cuban Missile Crisis contest.
Lesson: putting a line in the sand (or in this case the sea) is dangerous because it reduces the scope of potential negotiation and makes war much more likely.
In particular, President Kennedy sought to block Soviet ships going to Cuba, but was careful to phrase the action as “quarantine” rather than “blockade.” Further, he indicated that only ships carrying offensive weapons would be turned back.
Achieving policy goals without going to war is not simply a matter of firmness, which if wielded too bluntly will back an adversary into a corner. As JFK dictated to himself on October 18, “I was most anxious that we not have to announce the state of war existing, because it would obviously be bad to have the word go out that we were having a war rather than a limited blockade for a limited purpose.” At the last minute, he even switched the interception radius from 800 to 500 miles after a Soviet ship crossed it.
The military was pushing him very hard to attack, either with missiles or an invasion. Curtis LeMay told Kennedy he was convinced that the non-military strategy would “lead right into war.” He believed that taking a “strong stand” was the only way to be sure the Soviet would back off. Providing diplomatic wiggle room, however, allowed for alternate strategies to be followed before the use of force. Refusing to draw a line in the sand meant that LeMay’s argument was proven to be exactly wrong, and Kennedy achieved his policy goal without escalation.
It does not take a genius to see how this applies to the current policy debate about the Middle East between Mitt Romney and Barack Obama. Romney talked incessantly and aggressively about a "red line" beyond which Iran would not be allowed to go, in a way that was Curtis LeMayish. He has since backed down a bit:
"I do not believe that in the final analysis we will have to use military action. I certainly hope we don't have to," he said. "I can't take that option off the table – it must be something which is known by the Iranians as a possible tool to be employed to prevent them from becoming nuclear. But I certainly hope that we can prevent any military action from having to be taken."
The difference is whether war is viewed as a first option, or as a last option. Making your adversary believe that war is inevitable is a poor way to address a crisis.