In much of life, but especially in foreign policy, a three-word question is crucial: But then what? That is approximately what Adm. Isoroku Yamamoto said when Japan’s government asked if he could stealthily take a fleet across the northern Pacific and deal a devastating blow to the U.S. fleet at Pearl Harbor.

Yes, Yamamoto said, if we can design some shallow-running torpedoes of the sort the British had used a few weeks earlier (Nov. 11, 1940) to cripple the Italian navy at Taranto. Then, Yamamoto said, I will range freely in the Pacific for perhaps a year. But then what?

Having studied at Harvard and served as a military attaché in Washington, he knew the United States and knew that his attack would produce an industrial superpower unified by rage. Japan’s defeat was assured on Dec. 7, 1941, not six months to the day later at Midway.

Iran has no comparable capacity for retribution. There are, however, reasons to worry about Iranian threats to the 40,000 U.S. military personnel in the region, Iran’s capacity for nihilistic attacks on global energy and commerce, and the tentacles of Iran’s international terrorism apparatus. It will be a major surprise if there is only a negligible surprise from Iran.

Possible reasons Donald Trump decided to join Israel’s attack include this: He saw the success of Israeli virtuosity and he hungered to jump in at the head of the parade. He is less a military maven than a drum major, and his public life of flippancies about serious matters has not earned him the benefit of any doubts.

Were Congress not controlled by Republicans he controls, it might bestir itself to investigate what U.S. intelligence agencies knew about how close Iran was to building a useable bomb and missiles capable of delivering it to a target. Shortly before the U.S. attacks, Tulsi Gabbard, the astonishingly unsuitable amateur confirmed by the Senate as director of national intelligence, said in March that Iran had not decided to produce a nuclear weapon. She was either incompetent or the intelligence services are. Will Republicans in Congress seek the president’s permission to inquire as to which it was?

Perhaps the other three (China, Russia, North Korea) members of the axis of disruption will be sobered by the demonstration of the U.S. ability and willingness to project power globally. Perhaps the president will reconsider his contempt for Ukraine and his indifference to its fate. And his equally obvious infatuation with Vladimir Putin, who has received substantial material assistance from Iran.

Israel has earned America’s unalloyed respect by its recent displays of an audacity commensurate with the dangers of living surrounded by genocidal aspirations. Israel in Iran has delivered a message to others who threaten its destruction: We take your words seriously. So seriously, Israel has departed from past practices.

In Tennessee Williams’s play “A Streetcar Named Desire,” the pathetic Blanche DuBois’s last line is plaintive: “I’ve always depended on the kindness of strangers.” The Jewish state’s founding in the wake of the Holocaust was a defiant proclamation: “Never again!” Never again would Jews depend on the kindness of others.

In its War of Independence (1948), the Six Day War (1967), the Yom Kippur War (1973), and its unending conflict with non-state actors (the Palestine Liberation Organization, Hamas, Hezbollah), including the fourth major war, which began Oct. 7, 2023, Israel has had material, financial, and intelligence assistance from others, but has always done the fighting. Its major departure from this policy, the 1956 British-French-Israeli attempt to seize the Suez Canal that Egypt had nationalized, was a debacle.

By joining Israel against Iran, the United States has expanded its commitments more than it can now know. The United States is waging only a proxy war in Ukraine, but its prestige and credibility are fully at risk there. And now the United States is a participant in a war the likely outcome of which is obscured by the fog of war, and the momentum and direction of which is being set by an ally that has its own agenda.

Adolf Hitler reportedly said to one of his private secretaries, “The beginning of every war is like opening the door into a dark room. One never knows what is hidden in the darkness.” He supposedly said this as he prepared to do what he did 84 years ago last Sunday. He launched Operation Barbarossa, the invasion of Russia that proved his point.

U.S. Operation Midnight Hammer began Friday. Its reverberations are far from over.

George Will writes a column for the Washington Post.