Seven months later, on January 31, 1917, with World War I raging in Europe and prior to the United States entry into the war, Cukela enlisted in the United States Marine Corps.
He became a member of the 66th Company, 1st Battalion, Fifth Marine Regiment.

He was deployed to France in 1918 and fought in all the engagements in which the 5th Marines participated, from Belleau Wood to the Meuse River Crossing.
Along the way he earned a commission as a second lieutenant, as well as the Medal of Honor and four Silver Star Citations.
From the French, there was the Légion d'honneur, the Médaille militaire (the first award of this prestigious decoration to a Marine officer) and the Croix de guerre 1914–18 with two palms and one silver star.
Italy decorated him with the Croce al Merito di Guerra, while Yugoslavia weighed in with the Commander's Cross of the Royal Order of the Crown of Yugoslavia.

He was awarded the Medal of Honor by both the Army and the Navy (in the "Tiffany Cross" pattern) for the same action on the morning of July 18, 1918, near Villiers-Cotterets, France, during the Soissons engagement.
The 66th Company, 5th Marines, in which Cukela was then a gunnery sergeant, was advancing through the Forest de Retz when it was held up by an enemy strong point.
Despite the warnings of his men, the gunnery sergeant crawled out from the flank and advanced alone towards the German lines.
Getting beyond the strong point despite heavy fire, "Gunny" Cukela captured one gun by bayoneting its crew.
Picking up their hand grenades, he then demolished the remaining portion of the strong point from the shelter of a nearby gun pit.
He took four prisoners and captured two undamaged machine guns.

Cukela was wounded in action twice but since there is no record of either wound at the Navy's Bureau of Medicine and Surgery, he was never awarded the Purple Heart.
The first wound was suffered at Jaulny, France, on September 16, 1918, during the St. Mihiel engagement.
Cukela was wounded again during the fighting in the Champagne sector.
Neither wound was serious.

In addition to the two Medals of Honor, Cukela was awarded the Silver Star by the Army; the Médaille militaire (he was the first Marine officer ever to receive this medal), the Légion d'honneur in the rank of Chevalier, the Croix de guerre with two palms, another Croix de guerre with Silver Star, all by France; the Croce al Merito di Guerra by Italy; and Commander's Cross of the Royal Order of the Crown of Yugoslavia.
He also received three Second Division citations.

Cukela received a field appointment to the rank of second lieutenant in the Marine Corps Reserve on September 26, 1918, and was selected for a commission in the regular Marine Corps on March 31, 1919.
Promoted to first lieutenant on July 17, 1919, he was advanced to the rank of captain on September 15, 1921.
His promotion to major was effected on the day of his retirement, June 30, 1940.
Seven months later, on January 31, 1917, with World War I raging in Europe and prior to the United States entry into the war, Cukela enlisted in the United States Marine Corps. He became a member of the 66th Company, 1st Battalion, Fifth Marine Regiment.
He was deployed to France in 1918 and fought in all the engagements in which the 5th Marines participated, from Belleau Wood to the Meuse River Crossing. Along the way he earned a commission as a second lieutenant, as well as the Medal of Honor and four Silver Star Citations. From the French, there was the Légion d'honneur, the Médaille militaire (the first award of this prestigious decoration to a Marine officer) and the Croix de guerre 1914–18 with two palms and one silver star. Italy decorated him with the Croce al Merito di Guerra, while Yugoslavia weighed in with the Commander's Cross of the Royal Order of the Crown of Yugoslavia.
He was awarded the Medal of Honor by both the Army and the Navy (in the "Tiffany Cross" pattern) for the same action on the morning of July 18, 1918, near Villiers-Cotterets, France, during the Soissons engagement. The 66th Company, 5th Marines, in which Cukela was then a gunnery sergeant, was advancing through the Forest de Retz when it was held up by an enemy strong point. Despite the warnings of his men, the gunnery sergeant crawled out from the flank and advanced alone towards the German lines. Getting beyond the strong point despite heavy fire, "Gunny" Cukela captured one gun by bayoneting its crew. Picking up their hand grenades, he then demolished the remaining portion of the strong point from the shelter of a nearby gun pit. He took four prisoners and captured two undamaged machine guns.
Cukela was wounded in action twice but since there is no record of either wound at the Navy's Bureau of Medicine and Surgery, he was never awarded the Purple Heart. The first wound was suffered at Jaulny, France, on September 16, 1918, during the St. Mihiel engagement. Cukela was wounded again during the fighting in the Champagne sector. Neither wound was serious.
In addition to the two Medals of Honor, Cukela was awarded the Silver Star by the Army; the Médaille militaire (he was the first Marine officer ever to receive this medal), the Légion d'honneur in the rank of Chevalier, the Croix de guerre with two palms, another Croix de guerre with Silver Star, all by France; the Croce al Merito di Guerra by Italy; and Commander's Cross of the Royal Order of the Crown of Yugoslavia. He also received three Second Division citations.
Cukela received a field appointment to the rank of second lieutenant in the Marine Corps Reserve on September 26, 1918, and was selected for a commission in the regular Marine Corps on March 31, 1919. Promoted to first lieutenant on July 17, 1919, he was advanced to the rank of captain on September 15, 1921. His promotion to major was effected on the day of his retirement, June 30, 1940.
Louis Cukela