The full story of the seven resupply and rescue missions has yet to be told. But from exclusive interviews with two wounded survivors; a military intelligence officer who flew on the first mission; and pilot interviews provided by the Ukrainian army, The Associated Press has pieced together the account of one of the last flights, from the perspective of both the rescuers and the rescued.

Only after more than 2,500 defenders who remained in the Azovstal ruins had started surrendering did Ukraine’s President Volodymyr Zelenskyy first give wind of the missions and their deadly cost.

The Azovstal fighters’ tenacity had frustrated Moscow’s objective of quickly capturing Mariupol and prevented Russian troops there from being redeployed elsewhere. Zelenskyy told Ukrainian broadcaster ICTV that pilots braved “powerful” Russian air defenses in venturing beyond enemy lines, flying in food, water, medicine and weapons so the plant’s defenders could fight on, and flying out the injured.

The military intelligence officer said one helicopter was shot down and two others never came back, and are considered missing. He said he dressed in civilian clothes for his flight, thinking that he could melt into the population if he survived a crash: “We were aware it could be a one-way ticket.”