NEW YORK (AP) — George Vujnovich, the intelligence agent who organized a World War II mission to rescue more than 500 U.S. bomber crew members shot down over Nazi-occupied Serbia, has died at his home in New York. He was 96.

Vujnovich is credited with leading the so-called Halyard Mission in what was then Yugoslavia. It was the largest air rescue of Americans behind enemy lines in any war.

A long retired salesman of aircraft parts, he died April 24 of natural causes at home in Queens, according to his daughter, Xenia Wilkinson.

The Serbian-American and Pittsburgh native was an officer of the OSS, the precursor of today’s CIA, when about 500 pilots and other airmen were downed over Serbia in the summer of 1944 while on bombing runs targeting Hitler’s oil fields in Romania, according to U.S. government field station files.

The airmen were hidden in villages by Serbian guerrilla fighter Draza Mihailovich, leader of the Chetniks, whom Yugoslav communist officials considered to be Germany’s collaborators.

“This mission would not have succeeded without the great courage of Draza Mihailovich and his brave men,” Vujnovich said at a 2010 ceremony in which he was formally awarded the U.S. Bronze Star Medal.

It was no small feat to convince American officials to allow him to work with Mihailovich on the clandestine mission, dubbed Halyard, meaning a rope used to hoist sails. By then, President Franklin D. Roosevelt had decided to follow British Prime Minister Winston Churchill’s lead, abandoning support for Mihailovich in favor of the Yugoslav communists, the strongest grassroots guerrilla force fighting the invading Nazis and Italian fascists.