U.S. presidents who thought they could easily restrain Benjamin Netanyahu have quickly learned their lesson. “Who’s the (expletive) superpower?” Bill Clinton reportedly exploded after his first meeting with the Israeli prime minister.

Did Donald Trump make the same mistake? The U.S. State Department quickly declared that the devastating overnight Israeli attack on Iran — which killed key military commanders and nuclear scientists as well as striking its missile capacity and a nuclear enrichment site — was unilateral. Mr. Trump had reportedly urged Mr. Netanyahu to hold off in a call on June 9, pending U.S. talks with Iran over its nuclear programme due that coming weekend. The suspicion is that Israel feared that a deal might be reached and wanted to strike first. But Israeli officials have briefed that they had a secret green light from the U.S., with Mr. Trump only claiming to oppose it.

Iran, reeling from the attack but afraid of looking too weak to retaliate, is unlikely to believe that the U.S. did not acquiesce to the offensive, if unenthusiastically. It might suit it better to pretend otherwise — in the short term, it is not clear what ability it has to hit back at Israel, never mind taking on the U.S. But Mr. Trump has made that hard by threatening “even more brutal attacks” ahead, urging Iran to “make a deal, before there’s nothing left” and claiming that “we knew everything.” Whether Israel really convinced Mr. Trump that this was the way to cut a deal, or he is offering a post-hoc justification after being outflanked by Mr. Netanyahu, may no longer matter.

Israel has become increasingly and dangerously confident of its ability to reshape the Middle East without pushing it over the brink. It believes that its previous pummellings of Hamas, Hezbollah and Iran’s air defences have created a brief opportunity to destroy the existential threat posed by the Iranian nuclear programme before it is too late. Russia is not about to ride to Tehran’s rescue, and while Gulf states don’t want instability, they are not distraught to see an old rival weakened.

But not least in the reckoning is surely that Mr. Netanyahu, who survives politically through military action, only narrowly survived a Knesset vote last week.

The government also faces mounting international condemnation over its war crimes in Gaza — though the U.S. and others allow those crimes to continue. It is destroying the nation’s international reputation, yet may bolster domestic support through this campaign.

The obvious question is the future of a key Iranian enrichment site deep underground at Fordo, which many believe Israel could not destroy without U.S. “bunker busters.” If Israel believes that taking out personnel and some infrastructure is sufficient to preclude Iran’s nuclear threat, that is a huge and perilous gamble. This attack may well trigger a rush to full nuclear-armed status by Tehran — and ultimately others — and risks spurring more desperate measures in the meantime. Surely more likely is that Israel hopes to draw in Washington, by persuading it that Iran is a paper tiger or baiting Tehran into attacking U.S. targets.

“My proudest legacy will be that of a peacemaker and unifier,” Mr. Trump claimed in his inaugural speech. Yet on June 13 he said was not concerned about a regional war breaking out due to Israel’s strikes. Few will feel so sanguine.

The current incoherence and incomprehensibility of U.S. foreign policy fuels instability and risks drawing adversaries towards fateful miscalculations.