U.S. President Joe Biden flew into a still-reeling Israel today to deliver two crucial messages, one that will surely be welcome, another more difficult. Especially now, after an explosion at a Gaza hospital claimed the lives of possibly hundreds of Palestinians, he should ensure Israelis understand both are offered with a single aim in mind: to safeguard Israel and the lives of its citizens.

While Israel has blamed an errant rocket fired by Palestinian militants for the hospital tragedy, the incident has sparked protests across the region and raised the risk that Iranian proxies such as Hezbollah might join the fight. That makes it all the more important for Biden to reiterate the promise he made soon after the Hamas terrorist group killed at least 1,400 Israeli civilians and soldiers on Oct. 7: Israel doesn't stand alone against its enemies. Whatever the divides within Biden's Democratic Party, the ongoing dysfunction in the GOP, or former President Donald Trump's latest ravings, Israelis should know that the U.S. — as it has since the founding of their nation in 1948 — will brook no threat to the existence of their state.

The U.S. is already backing up that pledge with arms and advice, and is preparing to deploy medical personnel and other non-combat troops to Israel in case they're needed. Biden should leave no doubt that the potent naval and air units the U.S. has dispatched to the region will respond harshly if Iran or Hezbollah choose to escalate, regardless of the impact on oil prices or the administration's previous attempts to negotiate with the mullahs in Tehran.

The second message may not be so well received. As Biden has said, how Israel fights matters. Even before the hospital explosion, scenes of Palestinian civilians wounded, killed or driven from their homes had rapidly shredded sympathy for Israel's cause. To buy time, and to lessen the chances of the conflict spreading, it is in Israel's interests to minimize civilian suffering. It shouldn't be the one stopping humanitarian aid from reaching Gazan civilians or Gazans with foreign passports from leaving; its blockade of food, medicine, and fuel should be eased to prevent a public-health disaster. The butchers of Hamas will no doubt try to exploit any such effort for military ends. It's a risk worth taking nonetheless.

Just as important, Biden ought to remind Prime Minister Benjamin Netanyahu's unity government that real victory will come not when Hamas is defeated in Gaza, but when Israel has stable and secure relations with both its Arab neighbors and the Palestinians. Obviously, an attempt to revive the peace process at this moment — with Israelis fighting for their lives and facing a weak and ineffective negotiating partner in the Palestinian Authority — would fail and serve only to embitter both sides.

Even so, it's crucial that Israel's leaders think strategically. The Israeli army has no desire to reoccupy Gaza. Even if Israel were able to oust Hamas, it would then need help from Arab nations such as Egypt and Saudi Arabia to identify suitable Palestinian leaders, finance reconstruction and prevent a resurgence of militancy. Such support won't be forthcoming unless Arab leaders can demonstrate to their own people and to the wider Muslim world that Israel is ready to compromise for peace.

Both messages need to be conveyed with clarity and honesty. Israelis will surely give Biden a warm welcome. What he needs even more is a hearing.