Bruce Riedel of the Brookings Institution delivered a talk based on his article "If Israel Attacks" at the National Interest on Thursday that was illuminating, provocative--and dangerous. Essentially, Riedel argued that to avert a preemptive Israeli strike on Iran, the Obama administration should consider offering Israel a mutual-defense-treaty and a nuclear guarantee. He also believes that Washington should up its military cooperation with Israel to help ensure that it has a serious second-strike capability.

But would an American guarantee really carry much weight? During the cold war, America kept troops stationed in Europe. But that wasn't enough to ensure a credible deterrent, which is why Washington stationed tactical and intermediate-range nuclear weapons in Europe. Otherwise the deterrent wouldn't have deterred. Even then, it was somewhat of an open question whether America would really sacrifice Dubuque, Iowa in exchange for Berlin. It was the old question--mourir pour Danzig? Who will die for Danzig?

In South Korea, America keeps tens of thousands of troops deployed as a trip-wire. But the North's possession of nuclear weapons means that Washington proceeds extremely gingerly with the regime--precisely the outcome which Israel, bracing for another war with Lebanon, wants to avoid. Its manuevering room will be crimped once Tehran has a bomb.

Washington would have to station at least 10,000 soldiers in Jerusalem as hostages to persuade Iran that it was serious about hitting it in the event of a strike on Israel. But think about that from the Israeli viewpoint: it would crimp Israel's freedom of action. Any Israeli leader would have to worry about a military action--say, a strike on Lebanon--making American soldiers a target for Hezbollah. The American guarantee would become a pair of shackles rather than a liberating force.

As former ambassador Richard Burt observed, arms-control talks might be another way to address the problem. But Riedel wants to ramp up the number of arms going to Israel. He doesn't seem to think that this would help create a new arms-race. In his view, the Middle East is already in one. But his proposal would simply ramp it up to a new level.

Finally, there is the question of American credibility. Walter Lippmann warned about the dangers of taking on commitments abroad without actually possessing the ability to meet them--what he called the "commitment gap." Riedel's proposal would exacerbate that phenomenon. It would be nice if Israel's Iran problem could be neatly and surgically solved. But Riedel's proposed cure may be worse than the disease.