The U.S. launched airstrikes in eastern Syria Thursday night, marking the first public military operation of the Biden administration. President Joe Biden authorized the airstrikes on Iran-linked militias along the Syrian border with Iraq in response to recent attacks in Iraq on American and allied personnel. The Pentagon blames a recent attack on the Erbil airport in northern Iraq on Shia militants; t he Feb. 15 rocket attack killed a Filipino contractor and injured five Americans, including a Louisiana National Guard soldier and four other American contractors. Responsibility for the attack was claimed by Awliya al Dam, or Guardian of the Blood, a little known group.

The Pentagon said the American strikes, which took place at 2 a.m. Friday morning local time, successfully targeted a group of buildings at a border crossing used as an operational center for militia activity in neighboring Iraq. The Pentagon said the area was being used by two Iran-backed Iraqi militia groups, Kataib Hezbollah and Kataib Sayyid al-Shuhada. American officials emphasized that the strike was restrained and proportional, and largely meant to send a message as the Biden administration reengages with the Iranian regime on the nuclear deal that the U.S. reneged on during the Trump administration.

“The airstrike appears to be part of a U.S. message to Iran that it cannot improve its leverage in talks by attacking U.S. interests,” the Washington Post notes. “Some experts said the airstrike on Thursday signals a strategic middle ground that avoids further diplomatic strains with the Iraqi government, which assists the United States in the fight against the Islamic State and could view a strike in Iraq as a violation of its sovereignty.”