While Islamic State (IS) and its affiliates have carried out attacks from France to Afghanistan to the U.S., they have consistently refrained from attacking the Jewish state—even though their forces are, as one Israeli journalist put it, “several hundred meters away from reaching Israeli school buses.” Graham Allison explains how Israel’s strategy of patience and deterrence has succeeded, and urges America to take note:

Israel seeks to persuade IS not to attack it by credibly threatening to retaliate. If you attack us, the thinking goes, we will respond in ways that will impose pain that exceeds any gain you can hope to achieve. As cold-war strategists learned, making this work in practice is demanding. To be effective, deterrence requires three Cs: clarity, capability, and credibility. Specifically, this means clarity about the red line that cannot be crossed, communicated in language the adversary understands; capability to impose costs that greatly exceed the benefits; and credibility about the willingness to do so.

Failures occur when the deterrer falls short on any one of the three Cs. So, if I draw a red line, and you cross it, and I respond with words rather than the decisive punishment threatened, I fail the third C. Whatever excuse I give for not executing my threat, and however earnest my claim that next time will be different, the blunt fact is that adversaries will find my threats less credible. . . .

The flip side of the deterrence coin is an equivalent promise: if you refrain from the prohibited action, I will withhold the threatened punishment. If, for whatever reason, I decide to administer the specified punishment even though you have complied with my demands, I spend that coin—and can no longer use that threat to deter you. As the saying goes: if you’re damned if you do and damned if you don’t, then you might as well do.

On Tuesday, a Hizballah drone attack injured three people in northern Israel. The next day, another attack, targeting an IDF base, injured eighteen people, six of them seriously, in Arab al-Amshe, also in the north. This second attack involved the simultaneous use of drones carrying explosives and guided antitank missiles. In both cases, the defensive systems that performed so successfully last weekend failed to stop the drones and missiles. Ron Ben-Yishai has a straightforward explanation as to why: the Lebanon-backed terrorist group is getting better at evading Israel defenses. He explains the three basis systems used to pilot these unmanned aircraft, and their practical effects:

These systems allow drones to act similarly to fighter jets, using “dead zones”—areas not visible to radar or other optical detection—to approach targets. They fly low initially, then ascend just before crashing and detonating on the target. The terrain of southern Lebanon is particularly conducive to such attacks.

But this requires skills that the terror group has honed over months of fighting against Israel. The latest attacks involved a large drone capable of carrying over 50 kg (110 lbs.) of explosives. The terrorists have likely analyzed Israel’s alert and interception systems, recognizing that shooting down their drones requires early detection to allow sufficient time for launching interceptors.

The IDF tries to detect any incoming drones on its radar, as it had done prior to the war. Despite Hizballah’s learning curve, the IDF’s technological edge offers an advantage. However, the military must recognize that any measure it takes is quickly observed and analyzed, and even the most effective defenses can be incomplete. The terrain near the Lebanon-Israel border continues to pose a challenge, necessitating technological solutions and significant financial investment.