He trained as an illustrator at the Philadelphia Museum School of Art, where he studied under artists Karl Sherman, Henry C. Pitz, Albert Gold, Joe Krush and S. Gertrude Schell, and then graduated in 1953.

Soon thereafter, he was drafted into the U.S. Army and assigned to a military intelligence unit in Germany where he rendered images of Soviet weaponry, based on verbal espionage reports.

[1] A reviewer of Cohen's body of work noted that it both presented faithful depictions of aircraft and, more significantly, focused on the people involved and the emotional energy that they brought to their activities.

[1] His illustration work expanded to more mainstream clientele that included the U.S. Information Agency, the National Park Service, Paramount Pictures, Bantam Books, Harlequin Books, Random House, Holt Rinehart & Winston, Warner-Lambert, the U.S. Coast Guard, the National Guard Bureau, and the Boeing and Sikorsky Aircraft companies.

[1] In 1966, Cohen received an invitation to teach at his alma mater;[note 1] this led to a part-time position as an instructor and to increasing academic responsibilities.