Jack Lucas, 80, who at 14 lied his way into military service during World War II and became the youngest Marine awarded the Medal of Honor, died yesterday at a Hattiesburg, Miss., hospital.

He had been battling cancer, said his wife, Ruby.

Mr. Lucas, who stowed away aboard a Navy ship headed for combat in the Pacific Ocean, was just six days past his 17th birthday in February 1945 when his heroism at Iwo Jima earned him the nation's highest military honor.

He used his body to shield three fellow squad members from two grenades, and was nearly killed when one exploded.

"A couple of grenades rolled into the trench," Mr. Lucas said in an interview shortly before he received the medal from President Harry Truman in 1945. "I hollered to my pals to get out and did a Superman dive at the grenades. I wasn't a Superman after I got hit. I let out one helluva scream when that thing went off."

He was left with more than 250 pieces of shrapnel in his body, including six pieces in his brain and two in his heart, and endured 26 surgeries in the following months.

He was the youngest serviceman awarded the Medal of Honor in any conflict other than the Civil War. He became a symbol of patriotism in the decades after the war, meeting presidents and traveling the world to speak with frontline troops and fellow veterans.

He forged his mother's signature on an enlistment waiver and joined the Marines at 14. Military censors discovered his age through a letter to his 15-year-old girlfriend.

"They had him driving a truck in Hawaii because his age was discovered and they threatened to send him home," said D.K. Drum, who wrote Mr. Lucas' story in the 2006 book

Indestructible

. "He said if they sent him home, he would just join the Army and give the Army the benefit of his good Marine training."

After the war, he earned a business degree and raised, processed and sold beef in the Washington, D.C., area. In the 1960s, he joined the Army and became a paratrooper, Drum said, to conquer his fear of heights.