Jacobs participated in the Battle of Iwo Jima which began on February 19, 1945. On February 23 at 8 AM, First Lieutenant Harold Schrier, the E Company executive officer, led a 40-man combat patrol from Third Platoon, E Company, 2nd Battalion, 28th Marines up Mount Suribachi to siege and occupy the crest. Accompanying Schrier was Jacobs, a radioman from F Company who was assigned to him for the patrol. Schrier was to raise an American flag he was given to signal that the mountaintop was captured. Once on top of the volcano, a section of a Japanese water pipe was found that became the flagstaff for the flag. Schrier and two other Marines attached the flag to the pipe which was then carried to the highest spot on the crater.