The recent missile attack that targeted al-Qaida's No. 2 leader, Ayman al-Zawahri, is only the latest U.S. effort to kill senior jihadists. Among those who have been assassinated since Sept. 11 are al-Qaida's military chief, Mohammed Atef; its leader in Yemen, Qaed Sinan Harithi; and Abu Hamza Rabia, a senior operative in Pakistan.

But the Zawahri strike was different. Although the attack appears to have killed several senior militants, it missed Zawahri himself — and what's worse, it killed 18 civilians. After the attack, demonstrations erupted in several cities, and the Pakistani government issued a formal protest. Critics around the world demanded to know by what right the U.S. shot missiles into a sovereign nation; here at home, some wondered whether a policy of overseas assassinations could really be justified.

While these moral quandaries and political setbacks are relatively new for the Bush administration, they are by no means unprecedented. Targeted killing is a troublesome policy, one that often leaves doubt and confusion in its wake, and can create new problems in the place of old ones. Numerous questions are raised: What rules may a democracy play by? How far should it go in taking the fight to the enemy? What standards should it use to judge the propriety and effectiveness of its actions?

For decades, Israel has targeted a range of terrorist leaders (dramatically illustrated in Steven Spielberg's film "Munich"), and its experience offers lessons for the United States as it wades into these waters. In addition to killing several perpetrators of the 1972 Munich Olympics attack, Israel has killed leaders of the Palestine Liberation Organization, the Lebanese Hezbollah, Palestinian Islamic Jihad and Hamas.

After the second Intifada broke out in September 2000, Israel dramatically stepped up its targeting of Palestinian terrorists, killing more than 200 of them. This campaign worked. Targeted killings — combined with the border security barrier, military operations and improved intelligence — reduced Israeli deaths from a high of 172 in 2002 to fewer than 40 in 2005.

The targeted killing campaign also bolstered Israeli morale. In the last five years, Israel has lost more than 1,000 people to terrorism. No government can remain idle as its citizens are slaughtered, and, in a grim fashion, the killings of terrorists created a sense among the Israeli public that its government was striking back and protecting them.

Yet Israel's experience suggests many costs and limits to this policy. Most important, arrests are always preferable to killing. Moral considerations aside, arrests allow interrogation, and interrogation leads to information that can disrupt planned attacks or lead to the capture of other operatives.

And mistakes are inevitable. Although Israel often has superb intelligence, its operations at times produced results similar to the Zawahri strike.

In 2002, for instance, Israel set out to kill Salah Shehada, a senior Hamas operative. Shehada was a violent man who had directed as many as 52 terrorist operations, killing 220 civilians and 16 soldiers — and the Palestinian Authority had repeatedly refused to arrest him. Israel decided to do the job itself, but it called off its first eight attempts on Shehada's life because Israeli intelligence believed he was with his daughter.

But on July 22, 2002, when an Israeli F-16 finally dropped a 2,000-pound bomb on his apartment building, the operation went awry anyway. The strike killed Shehada, but it also killed 14 civilians, including his daughter and eight other children. International reaction to the attack was overwhelmingly negative; even the Bush administration called it "heavy-handed."

Targeted killings like the attempt on Zawahri should remain an option for the United States. Washington, D.C., must continue efforts to kill al-Qaida leaders in areas of the world where they cannot be arrested, the remote parts of Pakistan being perhaps the best example.

But a massive campaign like Israel's would be a mistake. Israel operates in a tiny area that it has penetrated with intelligence assets — and still, it has made mistakes. The U.S., in contrast, must operate globally and in regions where its intelligence is weak.

Alienating allies with killings gone awry could prove disastrous. The Pakistani government almost certainly signed off on the Zawahri strike — although it will not acknowledge that now — but continued mistakes would make it less likely to do so in the future. A decision by Germany, Malaysia or Morocco, say, to end cooperation could be devastating for U.S. counterterrorism efforts.

The U.S. has sought to build sympathy and support in the Muslim world, and targeted killings, especially when they go wrong, can be counterproductive. The bar for deciding whether or not to kill should thus be high.

Perhaps the biggest lesson the U.S. can draw from Israel is the need for transparency. Israel has a robust public debate on the controversial policy. While the government does not share specific intelligence, the targeting criteria are understood by all. The result is a broad consensus. In the U.S., in contrast, the process is secretive and, if mistakes occur, a backlash is possible. Although transparency might result in missed opportunities, the result would be a more sustainable policy.

Daniel Byman is director of the Center for Peace and Security Studies at Georgetown University and a senior fellow at the Saban Center for Middle East Policy. He wrote this commentary for The Los Angeles Times.