Sledge was enrolled in the Marion Military Institute but instead chose to volunteer for the U.S. Marine Corps in December 1942. He was placed in the V-12 officer training program and was sent to Georgia Tech where he and half of his detachment "flunked out" so they would be allowed to serve their time as enlistees and not "miss the war". Once he was out of school he was assigned duty as an enlisted man and was eventually assigned to K (King) Company, 3rd Battalion, 5th Marines, 1st Marine Division (K/3/5) where he served with Corporal R.V. Burgin and PFC Merriell "SNAFU" Shelton. He achieved the rank of Corporal in the Pacific Theater and saw combat as a 60 mm mortarman at Peleliu and Okinawa. When fighting grew too close for effective use of the mortar he served in other duties such as stretcher bearer and as a rifleman.
During his service, Sledge kept notes of what happened in his pocket sized New Testament. When the war ended, he took these notes and compiled them into the memoir that was to be known as With the Old Breed. After being posted to Peking after the war, he was discharged from the Marine Corps in February 1946 with the rank of Corporal.
After the war, Sledge attended Auburn University (then known as Alabama Polytechnic Institute) where he was a member of the Phi Delta Theta fraternity and received a Bachelor of Science degree in business administration in the summer of 1949. Sledge, like many other war veterans, had a hard time readjusting to civilian life. “As I strolled the streets of Mobile, civilian life seemed so strange,” Sledge wrote. “People rushed around in a hurry about seemingly insignificant things. Few seemed to realize how blessed they were to be free and untouched by the horrors of war. To them, a veteran was a veteran – all were the same, whether one man had survived the deadliest combat or another had pounded a typewriter while in uniform.”
Once an avid hunter, Sledge gave up his hobby. He found that he could not endure the thought of wounding a bird and said that killing a deer felt like shooting a cow in a pasture. His father found him weeping after a dove hunt where Sledge had to kill a wounded dove and in the ensuing conversations he told his father he could no longer tolerate seeing any suffering. A key turning point in his life and career followed when his father advised him that he could substitute bird watching as a hobby. Sledge started to assist the conservation department in its banding study efforts, the origin of his well-known passion for the science of ornithology.
When he came to enroll at Auburn University, the clerk at the Registrar's office asked him if the Marine Corps taught him anything useful. Sledge replied saying "Lady, there was a killing war. The Marine Corps taught me how to kill Japs and try to survive. Now, if that don't fit into any academic course, I'm sorry. But some of us had to do the killing — and most of my buddies got killed or wounded." He found his salvation in science, as it kept the flashbacks of Peleliu and Okinawa at bay. Close, constant study of nature prevented him from going mad; however, the war stayed with him, and finally at the urging of his wife, he began to put his thoughts on paper, at last allowing him to put his horrors behind him. He returned to Auburn in 1953 where he worked as a research assistant until 1955. That same year he graduated from API with a Master of Science degree in botany.
From 1956 to 1960 Sledge attended the University of Florida and worked as a research assistant. He published numerous papers on helminthology and in 1956 joined the Helminthological Society of Washington. He received his doctorate in biology from the University of Florida in 1960. He was employed by the Division of Plant Industry for the Florida State Department of Agriculture from 1959 to 1962.
In the summer of 1962, Sledge was appointed Assistant Professor of Biology at Alabama College (now the University of Montevallo). In 1970 he became a professor, a position he held until his retirement in 1990. He taught zoology, ornithology, comparative vertebrate anatomy and other courses during his long tenure there. Sledge was popular with his students, organizing field trips and collections around town. In 1989, he received an honorary degree and rank of colonel from Marion Military Institute. Eugene Sledge died after a long battle with stomach cancer in 2001. He was survived by his wife of nearly 50 years, Jeanne, and their two sons, John and Henry.
Sledge was entitled to campaign participation credit ("battle stars") for Capture and Occupation of the Southern Palau Islands (Peleliu), and Assault and Occupation of Okinawa Gunto
His decorations and medals include: