In one of the largest U.S. airstrikes in Yemen in months, “dozens” of al-Qaeda fighters were killed when American aircraft struck an al-Qaeda in the Arabian Peninsula training camp Tuesday morning, the Pentagon said.

Press secretary Peter Cook said that more than 70 AQAP fighters were using a training camp located in the mountains when it was struck. The operation used both manned and unmanned aircraft, added Chris Sherwood, a Pentagon spokesman.

“We continue to assess the results of the operation, but our initial assessment is that dozens of AQAP fighters have been removed from the battlefield,” Cook said in a statement.

The Pentagon’s justification for the strike was that it hindered AQAP’s ability to use the base to launch attacks against “U.S. persons.” Cook has used similar language to describe recent strikes in North Africa and the Middle East that have also targeted terrorist training camps.

Earlier this month, drones and fixed-wing aircraft launched a series of strikes against an al-Shabab training camp north of Mogadishu, Somalia, killing more than 150 people. In February, the United States attacked an Islamic State base in Sabratha, Libya, killing 49 — including one senior Islamic State fighter involved in the planning of multiple terrorist attacks in Tunisia.

According to a Long War Journal database, as of February this year, the United States has conducted 135 airstrikes in Yemen, including five strikes in 2016. According to the database, the United States has killed more that 650 AQAP fighters and 105 civilians. It is unclear whether Tuesday’s operation killed only enemy combatants.

AQAP has used Yemen as a base since the early 2000s and has been the focus of U.S. counterterrorism operations, including drone missions and a robust assistance package to the Yemeni government. However, with the outbreak of the civil war in 2015, U.S. operations in the country were suspended.

Forces from Saudi Arabia and a number of Persian Gulf states intervened shortly after the start of the conflict. With U.S. support, including munitions and refueling aircraft, the Saudi-led coalition has been primarily focused on fighting the Shiite Houthi rebels who seized power in Yemen while occasionally targeting AQAP fighters for nearly a year; there have also been reports that AQAP fought alongside Saudi-led coalition troops in the battle for the southern city of Taiz. And since the start of the civil war, AQAP has used the conflict to expand its area of operations and influence in the country.

Tuesday’s airstrike appears to be independent of the Saudi-led air campaign, although it is unclear if there was any coordination between the two countries.

In response to a question regarding U.S. and Saudi coordination, Sherwood wrote in an email that “the United States conducted this operation consistent with international law.”

This post has been updated.

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