“Trade wars are good, and easy to win.” So declared Donald Trump a few weeks ago, after announcing tariffs on steel and aluminum. Actually, trade wars are rarely good, and not at all easy to win — especially if you have no idea what you’re doing. And boy, do these people not know what they’re doing.

It’s odd, in a way. After all, trade is clearly an issue about which Trump is truly passionate. He tried to kill Obamacare, but to all appearances his main concern was tarnishing his predecessor’s legacy. He wanted a tax cut, but more to score a “win” than because he cared about what was in it. But reducing the trade deficit has been a long-term Trump obsession, so you might expect him to learn something about how world trade works, or at least surround himself with people who do understand the subject.

But he hasn’t. And what he doesn’t know can and will hurt you.

In the case of steel, here’s what happened: First came the splashy announcement of big tariffs, ostensibly in the name of national security — infuriating U.S. allies, which are the main source of our steel imports. Then came what looks like a climb-down: The administration has exempted Canada, Mexico, the European Union and others from those tariffs.

Was this climb-down a reaction to threats of retaliation, or did the administration not at first realize that the tariffs would mainly hit our allies? Either way, Trump may have gotten the worst of both worlds: angering countries that should be our friends and establishing a reputation as an untrustworthy ally and trading partner, without even doing much for the industry he was supposedly trying to help.