Taylor, who had met William J. Donovan briefly before the war, was then recruited to join the OSS, the United States' wartime intelligence agency established in 1942.

[4] In September 1943, Taylor was appointed OSS Operations Officer in Italy, where he set up a Maritime Unit branch in the city of Bari to supply Josip Broz Tito's Yugoslav Partisans, a guerilla force fighting against Nazi Germany in occupied Yugoslavia.

Taylor personally led many of the Maritime Unit's covert missions, including one into Albania to rescue a flight of American nurses and medics who had been forced down in the Ceraunian Mountains.

On a later trip, Taylor and his men were trapped in Albania for three months, sneaking back into Italy in July 1944 with letters from Albanian nationalist Abaz Kupi.

Suffering from dysentery and starvation, Taylor was scheduled to be executed four times, but was saved by fellow inmates who wanted him to survive to report on the camp conditions.

He was briefly reactivated in 1946 to serve as one of the primary witnesses in United States of America vs. Hans Altfuldisch et al.. During the trial, he detailed many of the atrocities committed by Waffen-SS members at the Mauthausen-Gusen concentration camp complex, based on the evidence he had helped to gather.