President Donald Trump just installed a mini-him as national security adviser. John Bolton, former U.S. ambassador to the United Nations, take-no-prisoners Fox News talking head, is now at the president's elbow as they confront some of the most corrupt and dangerous regimes in the world. Iran. North Korea. Russia.

Bolton's views are well-known and often mesh with Trump's. On the air and in the op-ed pages, he has argued forcefully that a pre-emptive strike on North Korea is "perfectly legitimate." He has long scoffed at the Iran nuclear deal, as has Trump, and urged the president to tear it up. He wants a tougher stance against Russia's aggressive military and geopolitical actions and policies; Trump has so far been reluctant.

Now Bolton will be front and center in talk — and action — on all fronts. The Iran deal could be history, abrogated by Trump in early May. The president is expected to meet North Korean dictator Kim Jong Un by the end of that month to talk about that country's rogue nuclear program. And Trump says he may parley soon with Russian Strongman-For-Life Vladimir Putin.

We don't know how the addition of Bolton and the subtraction of former national security adviser H.R. McMaster will change the equation. Another variable: CIA Director Mike Pompeo, who is poised to become secretary of state after Trump fired Rex Tillerson.

In sacking Tillerson and McMaster, however, Trump has silenced voices that had tried to mute some of his more bombastic foreign policy instincts, particularly on the Iran nuclear deal. What he'll hear from Bolton presumably will be much closer to what Trump himself has advocated. To what effect? The mercurial Trump reverses course and befuddles friend and foe with often contradictory stances on major issues within hours if not minutes of each other. Where he had voices advising calm, he now has a potential encourager-enabler.

But there's a mantra Trump should invoke when responding to advisers and weighing a case to confront an enemy or aid an ally: Suppose I do that. Then what?

Let's say Trump shreds the Iran deal. Then what? Does that raise or lower prospects that Iran will race to build bombs? What will allies like Great Britain and foes like Russia and China do? Will the U.S. be more or less secure?

Let's say Trump pre-emptively strikes North Korea. Then what? Will the North Koreans attack South Korea, potentially killing hundreds of thousands of civilians? Will they, can they, launch nuclear-tipped missiles toward Chicago and other U.S. cities?

These aren't implausible game-theory scenarios. These are possible real-world repercussions from provocative U.S. diplomatic or military maneuvering.

The U.S. national security adviser can't afford to indulge in let's-do-this-and-see-what-happens bluster. If a U.S. leader makes a threat, draws a red line or takes belligerent action, he'd better anticipate the ripple effects.

Leaders in capitals around the world may or may not believe what Trump — or any president — says. They know that the art of the bluff is part of the art of the deal.

But they do watch how a president changes his roster for clues about what he'll do next. They know John Bolton. And if Americans are wondering how Bolton will influence his boss, so are all those foreign leaders.

FROM AN EDITORIAL IN THE CHICAGO TRIBUNE