According to The Washington Post, Secretary of State Mike Pompeo delivered a message to Iraqi leaders, intended to be conveyed to Iran, that the deaths of any Americans would result in an American attack. In his tweets last week, Trump said Iran would never be allowed to get nuclear weapons. In his tweets today, Trump said any attack on “anything American” would draw an attack, although when Iran shot down an American drone, the president ultimately decided not to launch an attack in response, let alone to unleash “obliteration.”

In fairness to Trump, Iran is a foreign-policy puzzle that has confounded multiple American presidents. But Trump has made his own situation more difficult. His ranks of advisers are full of temps, including the secretary of defense. He doesn’t trust the advisers he has, speaking dismissively of National Security Adviser John Bolton in public (“John Bolton is absolutely a hawk. If it was up to him, he’d take on the whole world at one time, okay?”) and reportedly discarding his advice in private.

Read: Trump goes after Iran’s supreme leader

Presidents override the judgment of their aides all the time. The problem is that Trump doesn’t appear to possess the knowledge or judgment to formulate a policy independent of their advice, because he never bothered to learn about Iran in the first place. His policy from the start has been “Iran is bad, and Obama’s nuclear deal with Iran was bad,” and was formed largely from Fox News fulminations. This is fine as far as it goes, which is not very far. Trump’s lack of interest in boning up on the topics he deals with has popped up repeatedly, from health care (from “It’s going to be so easy” to “Nobody knew health care could be so complicated”) to border security to trade policy.

But that ignorance and indecision is nowhere so dangerous as when the nation stands on the brink of a shooting war. It’s impossible for Iran to know what the White House’s view is, raising the chances that it will miscalculate and set off an escalating conflict. While keeping the Iranians off guard might seem advantageous—Richard Nixon’s “madman theory”—the abortive strike means they may be confused but also less afraid. Meanwhile, there’s no way for allies to know how to support the U.S. position, which keeps changing. Not even the U.S. military knows what Trump wants.

Shrewd observers have warned for months that when Trump got into a genuine international crisis, he’d face a crisis of credibility: Americans wouldn’t trust his word, allies wouldn’t line up behind him, and adversaries wouldn’t take threats at face value. The confrontation with Iran shows some signs of being just such a crisis, but Trump has largely sidestepped the credibility problem by being totally incoherent. A policy can’t lack credibility if it doesn’t exist in the first place.