This week Israel's Iron Dome anti-rocket defense system scored its first successes against live enemy fire. Somewhat akin to the U.S. Patriot air defense system, Iron Dome uses radars and high-speed intercept missiles to knock incoming rockets out of the air. Amid the recent escalation of hostilities between Israel and Hamas, Iron Dome was deployed to defend southern Israel against rockets fired from the Gaza Strip. According to some reports, by early Saturday the system had shot down six rockets that had been directed at cities such as Beersheba and Ashkelon. This development is significant and deserves to be welcomed by many people, notwithstanding the views they may have about whatever else Israel does.

Israel does many things in the name of providing security to its citizens. Iron Dome is different in an important respect: It doesn't harm anyone. It only protects; it does not kill and it does not repress. Many of the other things Israel does in the name of security do harm others, sometimes grievously. The wall that has helped to keep would-be terrorist bombers from moving from the West Bank into Israel has sliced apart Palestinian communities, separating people's livelihoods from where they live. Other restrictions on Palestinians' daily movements have ended some livelihoods altogether. Embargoes of materials supposedly intended to prevent construction of military installations have prolonged squalor in the Gaza Strip. Operations aimed at killing accused terrorists have killed a good number of people not accused of anything. And some Israeli military operations have done this on a larger scale—most notoriously Operation Cast Lead in Gaza, which killed hundreds of Palestinian civilians.

The only way to find a possible disadvantage in an anti-rocket defense system would be to argue that by neutralizing one of the few means Palestinians have to strike back in response to Israeli actions, this gives Israel a freer hand to inflict even more damage. But it is hard to see how Israel would have any freer a hand than it does now to bash Palestinians, or to behave in any more unrestrained way than it does now. The effects of the rockets pale in comparison with the damage that Israel inflicts in the other direction, and the reflexive Israeli reaction to something like rocket fire has always been to strike back, immediately and hard.

In light of these considerations, the United States (and other outsiders) should do all they can to encourage the effectiveness of, and Israeli reliance upon, Iron Dome. The United States should be generous in assisting further development and improvement of the system, which Israeli officials cautiously describe as still only “experimental”. Outsiders have only limited means, of course, to determine how the Israelis set their priorities and allocate their resources. But the outsiders should use what means they have to influence Israel in the direction of more use of Iron Dome and any other undeniably defensive systems and less use of offensive, destructive measures. It would be great if somehow the Israeli Defense Forces could be induced to spend half their budget on Iron Dome.

Such an emphasis would do three things. First, to the extent that the system provides effective defense against rockets, it lessens the Israeli inclination to strike back with something like another Cast Lead. Second, it makes clear that when it really is the security of Israelis that is at stake—when it is a “pure play,” as investors would say, in Israeli security—there should be no question about outside sympathy and support. Third, it draws a clear distinction between Israeli security per se, which is worthy of such support, and many other Israeli actions, which are more worthy of criticism and condemnation than of support. Those other actions include those other steps that are taken in the name of security but are disproportionately destructive and harmful. And they certainly include actions that do not contribute to security at all but are still harmful, with the continued colonization of occupied territories being the most flagrant example.