Reading James Mattis’s resignation letter, one gets the sense of our secretary of defense serving as a kind of Hans Brinker these past two years—holding his finger in the dike lest the floodwaters drown the town. This week, with the abrupt revelation that our troops will withdraw from Syria and its rumored sequel for our forces in Afghanistan, Mattis could no longer keep back the Trumpian tide.

He is leaving, he says, so that President Trump may have a successor whose views are more aligned with his.

And what are Mattis’s views? “My views on treating allies with respect and also being clear-eyed about both malign actors and strategic competitors are strongly held and informed by over four decades of immersion in these issues,” he writes. “We must do everything possible to advance an international order that is most conducive to our security, prosperity and values, and we are strengthened in this effort by the solidarity of our alliances.”

He says he agrees with Trump that we should not be the world’s policeman, which is, by the way, something nobody—not even us evil neocon hawk monsters—believes we should be. But he believes in treating allies like allies. And he is right to think that Trump does not seem to think that America has allies or needs allies.

The question now is whether Trump is on the verge of becoming a 21st Century cyber-age Jimmy Carter—doubting the value of American military power, assuming its use will only make things worse, and signaling to America’s adversaries a general retreat. Carter’s behavior in this regard led to a series of adventurous moves against the United States. From Central America to Cuba, from Iran to Afghanistan, Carter struggled to navigate the third and fourth years of his presidency because his own worldview suggested these things weren’t supposed to happen.

Trump is far more cynical in his worldview than Carter, but actions are actions. His calling card with his base is strength. But a series of pullouts from American commitments abroad, along with continued efforts to play footsie with North Korea and undermine of NATO, will not seem like strength to people across the globe who wish America ill.

The Mattis resignation signals Trump’s maturation as a foreign policy leader in the sense that he no longer seems to feel he needs to listen to anyone about the unintended consequences of his actions. He is taking the reins. But he’s never ridden a horse.