Yesterday, the IDF closed in on the city of Khan Younis, Hamas’s main center in the southern Gaza Strip, beginning what Chief of Staff Herzi Halevi has described as the “third phase” of the operation. Two days beforehand, giving a speech in the United Arab Emirates, Vice-President Kamala Harris declared, “Too many innocent Palestinians have been killed. Frankly, the scale of civilian suffering and the images and videos coming from Gaza are devastating.” Such comments echo those of other U.S. officials, in what seems like a coordinated effort to hamstring the Israeli offensive in southern Gaza.

But how many “innocent Palestinians” does Vice-President Harris believe to be the right number to be killed? The laws of armed conflict in fact help provide a way of answering that question, as Shlomo Brody explains, through the oft-misunderstood doctrine of proportionality. Moreover, he argues, excessive restraint poses dangers of its own, a lesson Israel might have learned during the second intifada, after buckling to similar U.S. pressure:

In September 2003, the Hamas leader Sheikh Ahmed Yassin gathered with all of his senior men in a three-story Gaza apartment building. . . . Yet Israel didn’t strike. Fearful of dozens of civilian casualties along with the local and international protests that would ensue, Prime Minister Sharon, at the urging of the army chief of staff Moshe “Bogie” Yaalon, called off an attack using a massive bomb to topple the building.

An alternative plan was hastily proposed to shoot a smaller missile to destroy the third floor, where intelligence officials speculated the meeting was taking place.

They guessed wrong. The meeting, it turned out, was on the first floor. . . . Within a few days, sixteen Israeli citizens were dead and another 75 wounded by two Hamas suicide bombers.

Israel’s decision not to act cost the lives of many innocent Israelis. Fears of “disproportionate” accusations led Israel to shirk its primary moral responsibility, which is to protect its own citizens from being murdered by terrorists.

On Yom Kippur, Hizballah fired over 200 rockets and drones at Israel, with one drone hitting a retirement home in Herzliya, miraculously without casualties. Yesterday, however, proved less lucky: a drone launched by the Iran-backed group struck a military base, killing four and injuring another 58, about twenty moderately or seriously.

This attack reflects Iranian strategy: Israeli defensive systems are strong, but so are Iranian drones and missiles, and with enough attacks some will get through. As Ariel Kahana writes, such an approach is consistent with Tehran’s desire to fight a war of attrition, denying Jerusalem the chance to strike a decisive blow. Kahana explains how the IDF might turn the tables:

It’s worth noting that Iran’s strategy of wearing down Israel and other U.S. allies in the region is not merely a choice, but a necessity. Militarily, it’s the only card left in Tehran’s hand. Iran neither desires nor possesses the capability to deploy ground forces against Israel, given the vast geographical distance and intervening countries. Moreover, while Israel boasts one of the world’s most formidable air forces, Iran’s air capabilities are comparatively limited.

Israel’s trump card in this high-stakes game is its unparalleled air-defense system. For years, Iran had counted on its network of proxy organizations to provide a protective umbrella against Western strikes. However, a year into the current conflict, this strategy lies in tatters: Hamas is reeling, Hizballah is on the back foot, and the various militias in Iraq and Yemen amount to little more than an irritant for Israel. The result? Iran finds itself unexpectedly exposed.

And when it comes to direct attacks on Israel, Iran’s options may be limited. Its October 1 attack, which used its sophisticated Fateh-2 missiles, was more effective than that in April, but not much more so:

Oded Eilam, drawing on his experience as a former senior Mossad official, . .  estimates [Iran’s] stockpile of these advanced weapons is limited to between 400 and 800. With 200 already expended in a single attack, Iran’s reserves of truly effective missiles may be running low. This raises a critical question: can Iran sustain a prolonged ballistic exchange with Israel? The numbers suggest it’s capacity for attrition warfare may be more limited than it would like to admit.