Thursday, the US military said it used precision airstrikes in eastern Syria in response to an attack by a drone that killed an American contractor and hurt five US service members.
A statement from the Department of Defense said that a one-way unmanned aerial vehicle hit a maintenance facility on a Coalition base near Hasakah in northeast Syria, killing one US contractor and injuring the others.
The Pentagon said the UAV attack also hurt another US contractor, and the US intelligence community thinks that the UAV came from Iran.
Defense Secretary Lloyd Austin said that, at the request of President Joe Biden, he had approved "precision airstrikes tonight in eastern Syria against facilities used by groups linked to Iran's Islamic Revolutionary Guards Corps."
"The airstrikes were done in response to today's attack and a series of recent attacks by IRGC-affiliated groups against Coalition forces in Syria," he said.
Hundreds of US troops are in Syria as part of a coalition fighting against the last members of the Islamic State (IS) group. Militia groups have often attacked these troops.
The US troops help the Syrian Democratic Forces (SDF), the de facto army of the Kurds in the area. The SDF led the battle in 2019 that drove IS out of the last pieces of land it had in Syria.
The Pentagon said that two service members who were hurt on Thursday were treated at the scene, while the other three troops and one US contractor were taken to Iraq for medical care.
"As President Biden has said, we will do everything we need to protect our people, and we will always respond when and where we want," Austin said.
Biden was already in Canada when the strikes were announced. He will meet with Prime Minister Justin Trudeau and give a speech to Parliament.
Last August, after several drones hit a coalition outpost without killing anyone, Biden ordered similar retaliatory strikes in the oil-rich Syrian province of Deir Ezzor.
On the same day as that attack, Iranian state media reported that a Revolutionary Guard general had been killed a few days earlier while "on a mission in Syria as a military adviser."
Iran says that its forces are in Syria because Damascus asked for them, and they are only there to help.
The United States considers the IRGC a terrorist group and has put it on a list of banned organizations.