As the humanitarian crisis in northern Iraq stretched for days this summer, a question hung in the air: Would the United States deploy troops and aircraft to evacuate thousands of members of a religious minority group who had fled to Mount Sinjar and its surrounding cliffs to get away from the Islamic State?

The issue was raised after U.S. troops flew helicopters and V-22 Ospreys into northern Iraq as the military sent troops in to assess the situation. Defense Secretary Chuck Hagel said at the time that Marines and sailors involved wouldn’t have a combat mission, but “there are some things we can continue to do.” A Pentagon official, Col. Steve Warren, said at the time that about four Ospreys were in Iraq.

It turns out the mission up for consideration at the time was far broader, however. Gen. James F. Amos, the Marine Corps commandant, told USA Today that the service was preparing for a massive evacuation of the minority Yazidis that would have included about 24 Ospreys. The mission would have included not only aircraft pulled off Navy ships in the Middle East, but additional Ospreys that had been flown out of Afghanistan to Kuwait, Amos said.

“The plan was to pick everyone off the mountain,”Amos told USA Today in an article published Wednesday. “It was going to be a ’round the clock operation.”

“It would have been the largest evacuation that I can think of,” Amos added. “It could have been very dangerous as well.”

The scope of such an operation, involving multiple squadrons of aircraft, would have made it exceedingly rare. And as the commandant suggested, it would have opened U.S. troops up to risks like potential ground fire; they also would have had to negotiate treacherous terrain around Mount Sinjar.

U.S. Special Forces eventually landed a team on the mountain to assess the danger, and discovered the situation was not as severe as previously thought, Rear Adm. John Kirby, the Pentagon press secretary, said Aug. 14. The U.S. military’s airdrops had helped supply the Yazidis, and airstrikes in the region enabled many of them to flee the region without harm. Discussions about an aerial evacuation were called off at that point, defense officials said.