Buckles, who also survived being a civilian POW in the Philippines in World War II, died peacefully of natural causes early Sunday at his home in Charles Town, biographer and family spokesman David DeJonge said in a statement. Buckles turned 110 on Feb. 1 and had been advocating for a national memorial honoring veterans of World War I in Washington, D.C.

Buckles lied about his age to join the army at age 16. The Missouri native was among nearly 5 million Americans who served in World War I in 1917 and 1918.