In December 2013, American troops aborted a rescue mission in South Sudan. Now, the U.S. Air Force finally has released additional details about the ill-fated operation.

They’re pretty frightening … and impressive.

On Dec. 21, three Air Force CV-22 Ospreys carrying commandos left Camp Lemonnier in Djibouti, bound for the city of Bor in South Sudan. Widespread violence in the country following an attempted coup d’etat had trapped American civilians.

At first, the Pentagon and Africa Command were vague about what happened next. An official press statement said the aircraft had come under attack by forces on the ground and four unidentified “service members” were wounded.

The unique tiltrotors landed safely in Uganda. Official spokesmen described the casualties as being “in stable condition” and said the injured had gone to Kenya for extra medical attention.

These paltry snippets of information didn’t suggest the situation had been especially serious. But now in a new official news piece, the Air Force describes a deadly serious chain of events that almost resulted in the destruction of the aircraft and the deaths of people aboard.

The operation kicked off according to plan. The CV-22s—which can fly like regular planes and land like helicopters—arrived on schedule at the United Nations compound in Bor, where the evacuees were sheltering.

The pilots from the 8th Special Operations Squadron then flew around the immediate area to check for any hostile fighters. The tiltrotors were about to land when someone attacked.