This book continues the stories of Marine Corps heroes that began in Volume III, Marine Corps Heroes 1898-1916 of the Marine Corps Biographical Encyclopedia. Volume IV covers the organization of the Fourth Marine Brigade for expeditionary duty with the American Expeditionary Forces in France during World War I, and the brigade’s battles in the Toulon Defensive Sector and at Chateau-Thierry and Belleau Wood. Unlike the previous volume, which covered eight armed conflicts over a period of 18 years, this volume focuses on the five-week Battle for Belleau Wood, France, 31 May to 26 June 1918. The Battle for Belleau Wood stands with Guadalcanal, Tarawa, Iwo Jima, Chosin Reservoir, Khe Sanh, Hue, and Fallujah as one of the Marine Corps’ defining battles.The Marines who entered combat on 31 May 1918 were well-disciplined and highly motivated men who were inadequately trained in an obsolete tactical doctrine. They were not adequately prepared for the ferocity, tempo, and horror of the battle. They suffered staggering losses in the first three days of the battle because their senior leaders did not adapt to unforeseen battlefield conditions. Individual Marines made up for their senior leaders’ tactical deficiencies with extraordinary heroism, tenacity, and sacrifice. It was the junior officers, sergeants, corporals, and young privates who improvised new tactics and taught themselves how to maximize their firepower to defeat the interlocking fires of German machine guns in order to survive and win in a battle like no other in Marine Corps history.Some of the 165 Marine heroes in this volume are mentioned in standard Marine history books for their heroic actions in combat or their subsequent accomplishments in World War II, but no historian has written the full stories of their military service. However, most Marines in this volume were “ordinary” and long-forgotten men who performed extraordinary acts of heroism in the greatest battle the Marine Corps had ever fought—the Battle for Belleau Wood.