President Trump’s decision to promote Mike Pompeo to secretary of state is a huge step in the right direction. It means that, if Mr. Pompeo is confirmed, the administration will have in the top foreign policy job an officer who was first in his class at West Point, served as an officer of armor in Europe, soared at law school, mastered politics in Congress, has run the Central Intelligence Agency — and who agrees with the president.

What a contrast with Secretary Tillerson. The ex-chairman of ExxonMobil had some wonderful instincts (such as his plan to cut the State Department budget by 30%). He was, though, hobbled from the start by being described as the “adult in the room,” as if the President of America were a child. Plus, he turned out to be crosswise with Mr. Trump on an array of major issues.

As impossible situations go, it reminds us of the truncated tenure of President Reagan’s first state secretary, Alexander Haig. He seemed to chafe not only on policy but at presidential authority (when Reagan was shot, Haig tried to calm his countrymen by telling the press “constitutionally, gentlemen, you have the president, the vice president, and the secretary of state in that order” and assuring them that he was “in control” at the White House).

Mr. Tillerson never made a blunder quite like that, though Mr. Tillerson’s crack about the president being a “moron” was right up there. He evinced too often the need to state that he was there to do what the president wanted. That only underscored that he’d wanted to stay in the Paris climate accord, certify that Iran was in compliance with the Obama nuclear deal, and keep our Israel embassy in Tel Aviv.

Mr. Pompeo’s comparative advantage is illustrated by Bloomberg’s star columnist, Eli Lake. Mr. Pompeo saw the Iran pact’s problems so clearly that even when he was in Congress, representing a district in Kansas, Mr. Lake writes, he met with European bankers, diplomats and businessmen to warn them that investing in Iran was not as safe as Secretary of State Kerry was trying to get them to believe.

Mr. Pompeo also wrote for Foreign Policy a piece called “Friends Don’t Let Friends Do Business With Iran.” At the time, Mr. Lake writes, “one European diplomat told me his country was taking its cues from the outgoing Obama administration on investment in Iran. Now it will be taking cues from the man who tried to warn them about this.” Mr. Pompeo strikes us as an ideal type for Mr. Trump.

Particularly as Mr. Trump prepares to go to the summit with Kim Jong Un. He’ll need a top aide who understands deep down the danger of the Iran appeasement. The big danger at the Korean summit, after all, is not that we fail to come to terms. It’s that we accept terms that would leave North Korea under the heel of a communist dictatorship. The temptations are going to be enormous.

This is a time to remember Reykjavik. That’s when President Reagan, at the summit with the Soviet Party boss, Mikhail Gorbachev, refused to abandon our Star Wars missile defense. It’s a time to go back and read Ken Adelman’s masterful telling of the story of how Reagan stunned the world by standing up and walking out. And how it was refusing a deal that opened the way to our victory in the Cold War.