Arthur Jackson graduated from high school in 1942, then got a job as a laborer at the Naval Air Station in Sitka, Alaska. That December, he traveled down to Portland, Oregon, to enroll in the Navy's flight training program, but was turned down because of poor vision in one eye. The Navy recruiter suggested that he consider the Marine Corps. He signed up in January 1943.

He eventually joined the 17th Replacement Battalion and was sent to Australia. In Melbourne he was assigned to the Seventh Marines and served in the machine-gun section of a weapons platoon, which took part in the invasion of New Britain in December. The Seventh Marines then went on to the Russell Islands to prepare for the landing on Peleliu. At his request, Jackson was moved into a rifle platoon, where he became an automatic rifleman.

Jackson's unit landed on Peleliu on September 15, 1944, in temperatures topping 110 degrees. For three days, the Seventh Marines moved across the island. On the fourth day, Jackson's company was held up by sniper and machine-gun fire. His commander asked him if he thought he could make it to a shallow trench system that connected the enemy bunkers. Jackson's answer was yes. He lightened his load by removing his helmet, pack, and leggings; then, carrying a twenty-pound Browning automatic rifle and several magazines weighing one pound each, he headed directly toward the Japanese as his platoon laid down covering fire. Each time he got to an enemy position, he unloaded a full twenty-round magazine at it. By the time he finally reached the largest bunker, which held approximately thirty-five Japanese soldiers, his squad leader had brought up more ammunition and grenades, as well as a combat pack containing about forty pounds of explosives. Together he and Jackson prepared the charge. With his rifle, Jackson killed the two enemy soldiers guarding the bunker, then carried the charge of explosives to the aperture of the bunker and shoved it in, running for cover to a bomb crater about fifty yards away.

When all the debris from the explosion, including the huge coconut logs framing the bunker, had fallen to the ground around him, Jackson got up and took out the remaining enemy positions. In all, he accounted for the destruction of twelve pillboxes and fifty soldiers.

Four nights after this one-man assault, Jackson and his assistant automatic rifleman were in a defensive position when an enemy soldier lobbed a grenade into their foxhole. Jackson reached down and felt for it in the dark. When he stood up and tossed it back, killing two Japanese, he was hit in the neck by a stray .45-caliber bullet from a GI on the line. The slug came within a hair of his jugular vein. He was evacuated to a hospital ship bound for New Caledonia. After recuperating, he returned to his unit, eventually taking part in the invasion of Okinawa. A platoon sergeant by then, he was again wounded in action.

On October 5, 1945, Jackson received the Medal of Honor from President Harry Truman along with thirteen other men, including fighter ace Gregory "Pappy" Boyington of the Black Sheep Squadron and future Marine Corps Commandant Louis Wilson. The next day the group went to New York City for a ticker-tape parade in honor of Admiral Chester Nimitz.