Israel and the U.S. Need to Get Tough on Egypt Cairo has turned a blind eye to Hamas’s tunneling and shipments of weapons over and under its border.

Israeli and American officials long operated under the false assumption that the Egyptian army’s loathing of the Muslim Brotherhood and its offshoots—including Hamas—would keep in check the army’s corruption and anti-Israeli bias.

It would be naive to believe that the Gaza war has changed Egypt’s calculations. Though the conflict has disrupted the region, Egypt stands to gain from the disruption in some respects. For one, the war and shipping troubles in the Red Sea, where Iranian-aided Houthis routinely fire on ships, made it easier for Cairo to obtain $5 billion from the International Monetary Fund to offset the crushing debt Mr. Sisi has incurred through a spending spree by framing it as aid to an economy under pressure by the war.

Israeli military actions in Gaza haven’t so far ignited serious opposition among Egyptians to Egypt’s military junta, which for years has maintained a cold peace with Jerusalem. But that peace doesn’t imply that Egypt views Israel favorably. The Egyptian army, like the Hashemite monarchy in Jordan, learned years ago that peace treaties with the Jewish state don’t require a full-faith renunciation of anti-Zionism.

Through such agreements, Arab rulers have taken more from the U.S. than they’ve given to Israel. Since the Camp David Accords in 1978, according to the State Department, the U.S. has given Cairo more than $50 billion in military aid and another $30 billion in economic assistance. If Hamas survives the conflict—which seems likely—and controls the Egypt-Gaza border, the Egyptian military could profit through illicit trade. Egyptian public opinion will again put up with willful blindness at the border.

Neither the U.S. nor Israel has been willing to put Mr. Sisi’s feet to the fire over lax surveillance of border crossings and tunnels into Egypt. Before Oct. 7, Israeli officials knew that something suspicious was happening at the border, but few grasped the magnitude of the tunneling and armaments delivered. Since the massacre, Israeli and American officials have played down the Egyptian military’s culpability and nefarious inclinations. Instead, they’ve reverted to past habits: treating Egypt as an economic basket case and the army as the only bulwark against state collapse or another Islamist resurgence. This approach has effectively neutralized censure in Washington and Jerusalem while indulging Egyptian dysfunction.

Admitting the gravity of the problem could force the White House to accept permanent Israeli control of the Philadelphi Corridor, the narrow belt of land on the border between Gaza and Egypt. Even Israeli governments that embraced the two-state solution insisted on Israeli control of the West Bank’s ports of entry and the Jordan Valley. An Israeli admission of Egyptian culpability would allow Jerusalem to plan openly to keep control of a slice of Gaza, which would surely entail military deployments larger than Israeli politicians and generals want to accept.

U.S. and Israeli planning for what might happen in Gaza “the day after” has remained vague because all options are unrealistic, unappealing or both. Neither the Americans nor the Europeans, whom the Israelis might trust to monitor the Egypt-Gaza border, are going to volunteer for what likely would be combat duty. Egypt, Jordan and the Arab nations of the Abraham Accords aren’t going to volunteer to kill Palestinians. Neither will the Palestinian Authority, which seems to have become even less popular in the West Bank since the Gaza war started. And there’s no way that Israelis will trust Fatah, the Palestinian Authority’s military muscle, which hasn’t confronted Hamas since Oct. 7, to monitor the Egyptian border.

No matter what the Israelis end up doing in Gaza, Washington should get serious about Cairo’s behavior. Through decades of greed and central planning, the Egyptian army has impoverished Egypt and continually turns to other countries for bailouts. Neither Russia nor China will give Egypt something in exchange for nothing. Neither Saudi Arabia nor the United Arab Emirates, off whom the Egyptians try to leech, has the means or desire to save Cairo from dysfunction. By contrast, Washington has the means and the will to help Cairo, and it should use that leverage to do a lot more arm-twisting of the Egyptian military. The U.S. and Israel have nothing to lose and more than a little to gain.

Mr. Gerecht is a resident scholar at the Foundation for Defense of Democracies and member of the bipartisan Egypt Working Group.