QAMISHLI, Syria — When the international manhunt for Abu Bakr al-Baghdadi, the leader of the Islamic State, zoomed in on a village in northwestern Syria, the United States turned to its local allies to help track the world’s most-wanted terrorist.
The American allies, a Kurdish-led force that had partnered with the United States to fight ISIS, sent spies to watch his isolated villa. To confirm it was him, they stole a pair of Mr. al-Baghdadi’s underwear — long, white boxers — and obtained a blood sample, both for DNA testing, the force’s commander, Mazlum Abdi, said in a phone interview on Monday.
American officials would not discuss the specific intelligence provided by the Kurds, but said that their role in finding Mr. al-Baghdadi was essential — more so than all other countries combined, as one put it — contradicting President Trump’s assertion over the weekend that the United States “got very little help.”
Yet even as the Syrian Kurdish fighters were risking their lives in the hunt that led to Mr. al-Baghdadi’s death this weekend, Mr. Trump abruptly shattered America’s five-year partnership with them.