Butler did not say whether Milley met with commanders of the Kurdish-led Syrian Democratic Forces that have been the main ally of U.S. forces in Syria in the fight against IS.
Milley’s visit came a day after the U.S. Central Command said American troops and their allies carried more than a dozen joint operations in northeast Syria in February during which five IS operatives were killed and 11 detained.
“While there, he received updates on the counter-ISIS mission, inspected force protection measures and assessed repatriation efforts for the Al Hol refugee camp,” Butler said referring to a camp housing tens of thousands of mostly IS-linked women and children.
At al-Hol, tens of thousands of Syrians and Iraqis are crowded into tents in the fenced-in camp. Nearly 20,000 of them are children; most of the rest are women, wives and widows of IS fighters.
In a separate, heavily guarded section of the camp known as the annex are an additional 10,000 people: 2,000 women from 57 other countries — they are considered the most die-hard IS supporters — along with about 8,000 of their children.
Over the past few months several countries, including France, Spain and Iraq, repatriated scores of women and children from al-Hol.
Kurdish authorities currently operate more than two dozen detention facilities scattered across northeastern Syria, holding about 10,000 IS fighters. Among the detainees are some 2,000 foreigners whose home countries have refused to repatriate them, including about 800 Europeans.
There are currently about 900 U.S. forces on the ground in northeast Syria, according to Deputy Assistant Secretary of Defense Dana Stroul.
Despite their defeat in March 2019 during which IS lost the last sliver of land it once controlled, the extremists sleeper cells still carry out deadly attacks in Syria and neighboring Iraq.
In February, IS sleeper cells attacked workers collecting truffles near the central town of Sukhna, killing at least 53 people, mostly workers but also some Syrian government security forces. Several similar attacks have occurred since.
Baldor reported from Washington.