Trump just stepped into dangerous waters.

When the president said on Thursday that the U.S. would pull out of Syria “very soon,” in another apparently off-handed (and definitely off-script) quip, it struck to the very heart of why some American troops had said they voted for him — and why they had said they would never vote for Hillary Clinton.

Back during the campaign, more than one special operator said to me privately that they were worried Clinton “would get us killed.” That’s not hyperbole. That’s a quote.

What they meant was that they expected a trigger-happy President Clinton would increase their missions, while the more-isolationist President Trump would not.

On Thursday, Trump said: “We're knocking the hell out of ISIS. We'll be coming out of Syria, like, very soon. Let the other people take care of it now. Very soon … we’re going to be coming out of there very soon."

That has to send chills down the spines of a lot of Green Berets and other elite coalition forces who have fought, bled, and died to win back that territory — and who are saying the U.S. needs to stay until a peace is settled, just like Gen. Joseph Votel, commander of U.S. Central Command, said as recently as January.

The argument went like this: Hillary was a known war hawk who would start new wars, continue current wars, and send more special operations troops into additional counterterrorism missions. Clinton had a record of defending U.S. military interventions and active engagements abroad and promising to continue a strong U.S. military posture abroad if she were elected. No argument there. But these troops and fighters also felt that Clinton would want to start wars and send troops as a political distraction to prop herself up and distract the public from her undoubtedly unpopular domestic standing and agenda that would come. That hypothesis is pure wag-the-dog conspiracy theory speculation, frankly, but it’s what they told me they believed and it is just one reason they did not want to vote for her.

Part of this fear was based on their own experiences. The most frequent criticism of President Obama’s stewardship of Iraq is that he pulled U.S. troops out of the country, and those that fought and died there did so in vain — only to be sent back to cover for his mistake. And they were weary of the Afghanistan war, too. They told me they believed that Clinton, too, would send them off fighting and dying for yet more pointless gains that Washington politicians eventually would give away — like miniature Iraq wars, all over the place.

It wasn’t even as much as an indictment of Clinton as it was about their perception of the entire U.S. national security modus operandi of the past 15 years: send us, kill or get killed, hope for a political ending, watch it fall apart, pull us out, and then send us back in again to fight for the same terrain. Just look at some of the commentary from Iraq veterans on the 15th anniversary of the war, last week, like Andrew Exum’s “What Were We Doing in Iraq, Anyway?” That’s the exact attitude — and fear — of today’s troops fighting in Syria, which Trump indicated to his cheering fan base that he’s eager to walk away from as soon as possible.

During the 2016 campaign, two years ago now, many were being asked to head back into Iraq and into Syria, into dangerous missions where U.S. casualties were beginning to reoccur with more frequency. They, too, didn’t want to be sent into military adventurism. They didn’t want their friends to die in vain.

Related: ‘I Want to Finish This’: US Special Ops Leaders Urge Washington to Stick by the Syrian Kurds

It’s all partly why, when I went with Votel to Iraq, Syria, Afghanistan, and four other countries in the Middle East in January, I kept asking him and other senior military commanders to explain to Americans back home why they should still believe in the mission — why those U.S. military interventions were worth it. The Trump administration has not made clear their plans for the future of counterterrorism missions that are increasing in frequency across North Africa, or whether the Pentagon has the personnel and resources to achieve them. Today’s commanders have clear answers for why the U.S. military should stay in Iraq, Syria and Afghanistan. They have less clarity on what they’re doing in Africa, or at least how much for how long.

Related: Meet the Believers: The Afghanistan War’s US Commanders are Ready For a Reboot

Related: The War in Iraq Isn’t Done. Commanders Explain Why and What’s Next

“The world is a big place,” Gen. Robert Neller, commandant of the Marine Corps, told me on Thursday, in an interview at the Atlantic Council, in Washington. I asked him if the U.S. had the resources for counterterrorism across Africa at the level some are predicting. “We don’t have enough capacity to do it all by ourselves, and nor should we want to do it by ourselves,” he said. (Full video here.)

Instead the U.S. and allies should continue training local forces, expecting short-term missions here and there. “At the end of the day, we can’t stay there. … We can train them, we can episodically go visit them, but we don’t need to stay there.” That’s the balance of the capacity of the military and requirements put on it by civilian leaders. It also means there will be a lot of battles in the global war on terrorism where some gains may be short-lived.

That’s neither Trump- or Clinton-specific. But the president, with one quip, potentially has turned the entire U.S. participation in the ISIS war in Syria into just that: short-term adventurism. Right or wrong, Trump views the military as the hammer for terrorism’s eternal whac-a-mole game. He loves to go after the bad guys as much as he wants to get out quickly and let the locals sort out their own mess. Trump ignores the basic idea behind counterterrorism warfare that U.S. commanders so often preach: that the absence of security and good governance is what breeds terrorism — especially the kind that is focused on attacking targets in the U.S. and Europe.

Trump draws big cheers when he talks about sending U.S. troops to kill ISIS. He draws equally big cheers when he talks about pulling them home. Those doing the killing, and dying, will have to reconcile with that — and whether the mission yet another president has sent them to do is worth getting killed over.