When it comes to Iran, is Trump a man without a plan?

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This is known: Iran’s theocratic government is under siege from protesters. An American strike force, including three destroyers with missile-launch capabilities, is within range of Iran. Iran’s nuclear team is burrowing deeper into the earth to safeguard its weapons operations from further air attacks. Donald Trump is emboldened by the American effort to produce the sinews of regime change in Venezuela.

This is unknown: Mr. Trump’s real plans. Whether the mobilization of a U.S. military force that the President called an “armada” is a negotiating tactic or a prelude to further attacks. Whether any American military action would include troops on Iranian soil. What Iran’s response would be, against Israel and against American installations and the more than 30,000 American troops in the region. What would follow a military attack. And whether a destabilized Iran would produce a destabilized Middle East.

“This could be a deliberate strategy to maintain ambiguity that would keep adversaries and allies off guard,” Eric Lob, a Florida International University expert on Iran and onetime visiting scholar at the University of Tehran, said in an interview. “Trump is tying this to nuclear negotiations so this may be the motivation. But with Trump there always could be other motivations. It is really unclear what the end game is here.”

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These uncertainties occur as the 47th anniversary of the return from exile of the Islamic Republic’s founder, Ayatollah Ruhollah Khomeini, approaches on Sunday, and as Reza Pahlavi, the eldest son of the U.S.-backed Shah who fled the country during the 1979 Iranian revolution, is becoming increasingly prominent with his calls for a secular democracy.

Both the United States and Canada have declared Iran a state sponsor of terrorism. Canada has sanctioned more than 210 Iranians and 254 Iranian entities, and a former Canadian minister of justice, Irwin Cotler, has been targeted for assassination by Iranian agents.

The latest flare in relations between Iran and the United States came amid demands for fruitful negotiations from Mr. Trump, who this week threatened military intervention “with speed and violence” unless Iran undertook to “negotiate a fair and equitable deal” leading to the cessation of its nuclear-weapons effort. Mr. Trump ordered a massive attack on Iranian nuclear facilities in June.

The recent mobilization has moved American military assets, including the aircraft carrier Abraham Lincoln and attack planes and fighter jets, closer to Iran. The June attack underlined the capacity of U.S.-based long-range aircraft to wreak significant damage; the B-2 stealth bombers that hit the Fordow and Natanz nuclear facilities originated in Whiteman Air Force Base in Missouri, more than 11,000 kilometres away.

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Mr. Trump, who did not seek either permission or forbearance from congressional leaders for the initial Iran attack, has not consulted with officials on Capitol Hill this time either. The War Powers Act provides some limitations on presidential prerogative, but Mr. Trump’s predecessors, who operated with legislative branches far more protective of their foreign-policy prerogatives than the current 119th Congress, routinely have taken action similar to what the President is contemplating without legal sanctioning or political damage.

And while Mr. Trump’s MAGA base was built on substantially limiting American overseas involvement, and pointedly opposes nation-building efforts, the regime of Ayatollah Ali Khamenei may be regarded as sufficiently odious that the President’s supporters may not find an American incursion repellent. The crackdown on Iranian protests this month may soften Democrats’ reflexive opposition to Mr. Trump’s initiatives, though it is almost certain that his opponents may stress the incongruity of his support for dissent in Tehran with his opposition to it in Minneapolis.

However, these Trump skeptics and opponents, and many of his supporters, may express concern that the White House has not provided a broad strategic plan for U.S. relations with Iran, nor a specific rationale for even contemplating military action.

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Two prominent military strategists in Republican presidencies have warned against impulsive military intervention without the establishment of specific goals and the laying out of action plans that follow military strikes.

The Weinberger Doctrine, developed by Defense Secretary Caspar Weinberger (1981-1987) in the Ronald Reagan administration, calls for the commitment of U.S. combat troops “only with clearly defined political and military objectives and with the capacity to accomplish those objectives” and only with “a ‘reasonable assurance’ of the support of U.S. public opinion and Congress.”

The Powell Doctrine, promulgated by Colin Powell, chairman of the Joint Chiefs of Staff in the George H.W. Bush administration during the run-up to the 1990–1991 Gulf War (and later Secretary of State in the George W. Bush administration), required an assessment of whether any military action was addressing a threat to a “vital national security interest”; whether there is “a clear, attainable objective”; and whether there is “a plausible exit strategy.”

But it may be the counsel from a third Republican president, issued when he was a House of Representatives opponent to the Mexican War being undertaken by James K. Polk – the chief executive Mr. Trump has cited in his effort to win Greenland – that may be just as relevant to the current situation in Iran and to the sitting president.

“Allow the President to invade a neighboring nation, whenever he shall deem it necessary,” Mr. Lincoln wrote to William Herndon, his law partner, “and you allow him to make war at pleasure.”