A humanitarian disaster is unfolding in southern Syria, where hundreds of thousands of people are fleeing heavy fighting and finding borders locked tight. More than three hundred thousand civilians are on the move—some on tractors, some on foot—trying to escape a Russian-backed Syrian Army offensive aimed at reconquering the city of Dara’a and the surrounding area, where the rebellion against the regime of Bashar al-Assad began seven years ago.

The refugees are fleeing Dara’a in two waves: to the east, toward the nearby Jordanian border, and to the west, toward Israel. Both borders are closed, and the refugees are piling up at the frontiers. The Kingdom of Jordan, which has already taken in nearly a million and a half Syrians, fears that to take in any more would put its very survival at risk. (Jordan’s total population is about ten million.) For its part, Israel has accepted almost no Syrian refugees since the war began. Both countries are providing some help to those fleeing—the Jordanians inside a “safety zone” within their own territory, where other relief groups are also operating, the Israelis by sending relief supplies to camps across the border and by treating small numbers of Syrians in Israeli hospitals. It’s better than nothing, but, against the need, hardly enough.

As a result, this latest wave of displaced Syrians, who number three hundred and twenty-five thousand, are withering in the sun; most have no shelter, food, or water. Daytime temperatures are nearing a hundred degrees. Women on the run are giving birth; children are dying not just from dehydration brought on by diarrhea but from scorpion bites. “They’re in desert-like conditions,” Paul Donohoe, a spokesman for the International Rescue Committee, told me. “And the doors are closed.” Among its efforts, the I.R.C. has put a midwife in a mobile clinic just inside the Jordanian border to help deliver babies. Esraa al-Amer, a twenty-two-year-old Syrian woman, made it to the Jordanian safety zone with her two children. The Russian bombs, she told Al Jazeera, were falling “as if it were the Day of Judgment.” “We left everything and ran to the borders.”

The plight of the Syrians fleeing Dara’a is another sad example of America’s persistent reluctance to involve itself in the Syrian war. The rebellion began in 2011, following the castration and murder, by Assad’s goons, of a thirteen-year-old boy named Ali Hamza al-Khateeb, who had been detained for spraying anti-government graffiti. The Assad regime, now in its forty-seventh year, has sworn to crush the rebels, no matter how numerous they are; since 2011, at least four hundred thousand Syrians have died, and roughly half of all Syrians have fled their homes. As the war began, President Obama refused all but the most token support for the rebels battling Assad, fearing a quagmire. Iran, Russia, and Hezbollah rushed into the vacuum and saved Assad. During the 2016 Presidential campaign, Donald Trump criticized Obama’s Syria policy, but since becoming President he has more or less continued it.

Which brings us to Dara’a. Last July, President Trump and President Vladimir Putin of Russia agreed to a ceasefire in Dara’a and its environs. (King Abdullah of Jordan signed on, too.) They called it a “deëscalation zone.” At the time, the agreement was held out as a sign of how the United States and Russia could work together. “I would tell you that, by and large, our objectives are exactly the same,” Rex Tillerson, who was then the Secretary of State, said.

At the time, Assad’s Army was consolidating its gains in the north of the country, thanks in part to America’s offensive against ISIS. At the same time, Assad was preparing to launch a military campaign in Eastern Ghouta, a large rebel-held area in the Damascus suburbs. A ceasefire in Dara’a, the meddlesome southern province, fit Assad’s needs at the time perfectly. “The Syrians wanted the agreement to buy time,” Jennifer Cafarella, a Syria analyst at the Institute for the Study of War, in Washington, told me.

Assad’s reconquest of Eastern Ghouta was completed in April—with the help of chemical weapons—freeing up his Army to head for Dara’a. When the offensive began, two weeks ago, Russian officials, unleashing waves of air strikes, said they had decided to help the Syrian Army crush “terrorists.” There was no mention of the “deëscalation zone” that Trump and Putin had agreed to a year ago. The advance of Assad’s Army into Dara’a has also been aided by Iranian-backed militias. Several rebel groups have already surrendered.

There’s hardly been a peep out the Trump White House. The “deëscalation zone” was inaction disguised as action; indeed, for all of President Trump’s criticism of his predecessor, he has made it absolutely clear that he intends to stay out of Syria, even at the price of allowing Putin to make him look like a pathetic weakling. This is how Heather Nauert, the State Department spokeswoman, put it this week: “We’re continuing to have talks with the Russians, we’re continuing to have talks with the Jordanians, and express our extreme concern about the situation there.” Cafarella, the Syria analyst, put it more succinctly: “There was never any intention of enforcing the agreement.” On Friday, Syrian forces reached the border post of Nassib, giving them control of one of the main highways running between Damascus and Jordan.

Since 2011, American foreign policy in Syria has been a classic study in the lessons of Realpolitik: preserve the status quo and, above all, use your power only to advance your self-interest. Under both Presidents Obama and Trump, the United States has carried out those dicta perfectly—risking nothing, losing nothing. But Realpolitik has a price, too, even if it can’t be precisely measured in power and self-interest. The catastrophe unfolding in Dara’a is a reminder of just how much America has paid.