He enlisted in the IDF naval special forces unit of the Israeli Navy, Shayetet 13. After an injury, he moved to the Armored Corps, where he was trained as a fighter and in a tank commander's course. Subsequently he completed an Officers Course and was a tank commander. In Operation Litani (1978) Gendelman, as a company commander, led the forces in the occupation of the town Bint Jbeil. During the Lebanon War he was the brigade operations officer. At the end of the war he became 7th Armored Brigade officer and eventually the regiment commander. Gendelman served as commander of 460th Brigade and in 1996 was promoted to brigadier general, and was the bang division commander, and the commander of the company and battalion commanders course. In 1999, he was appointed as a commander of the 36th Division, having served in that capacity for two years.