Ahrens — born on 4 November 1919 in Dayton, Kentucky — enlisted in the United States Marine Corps on 3 February 1942 in Cincinnati, Ohio, and underwent boot camp training at the Marine Corps Recruit Depot Parris Island, South Carolina. He transferred to the Marine Barracks Quantico, Virginia on 16 March 1942.
Assigned to Company "A", 1st Raider Battalion, Fleet Marine Force, soon thereafter, Ahrens landed with that unit from Little (APD-4) at Tulagi, Guadalcanal, British Solomon Islands, in the second assault wave on 7 August 1942. With Company "C", 1st Raider Battalion, securing the right flank on the beachhead, Company "A" moved inland and down the right slope of Tulagi's central ridge. Initially, the Marines were not opposed.
That evening, Company "A" took positions for the night west of a cricket ground on the island, as part of the defensive line extending along the ridge. The Japanese later launched a fierce nocturnal counterattack which drove a wedge between the two Raider companies. Isolating the latter near the beachhead, the enemy concentrated his efforts on Company "A" in an attempt to sweep up the ridge toward the residency, a former British government building serving as a Raider battalion command post. The Raiders, however, stood firm.
During the savage battle that ensued, Ahrens, in a security detachment assigned the task of protecting the Raiders' right flank, singlehandedly engaged a group of Japanese in hand-to-hand combat as they attempted to infiltrate the Raiders' rear.
At morning's first light, Major Lew Walt walked his lines to assess Able Company's condition. "I came across a foxhole occupied by Private First Class Ahrens, a small man of about 140 pounds...He was slumped in one corner of the foxhole covered with blood from head to foot. In the foxhole with him were two dead Japs, a lieutenant and a sergeant. There were eleven more dead Japs on the ground in front of his position. In his hands he clutched the dead officer's sword."
Ahrens was dying from multiple gunshot and stab wounds. His last whispered words, according to Walt: "The bastards tried to come over me last night-I guess they didn't know I was a Marine." Private First Class Edward H. Ahrens, twenty-two, unmarried, from Dayton, Kentucky, died in Major Walt's arms.