Jacob Loucks Devers (; 8 September 1887 – 15 October 1979) was a general in the United States Army who commanded the 6th Army Group in the European Theater of World War II. He was involved in the development and adoption of numerous weapons, including the M4 Sherman and M26 Pershing tanks, the DUKW amphibious truck, the Bell H-13 Sioux helicopter, and the M16 rifle. A graduate of the United States Military Academy, Devers was commissioned in the field artillery in 1909. During World War I, he was an instructor at the School of Fire at Fort Sill, Oklahoma, and did not serve in France until after the November 11 armistice ended the fighting, when he attended the French artillery school at Treves. Between the two world wars, he was a staunch advocate of mechanization when the idea of phasing out horses met strong resistance from conservative gunners. When World War II broke out in Europe, Devers was stationed in Panama. He was promoted to major general in October 1940 and took command of the newly-formed 9th Infantry Division at Fort Bragg, North Carolina, a base whose construction he oversaw. Appointed Chief of the Armored Force in August 1941, he supervised its expansion from four armored divisions to sixteen. He was an articulate proponent of the emerging tactical doctrine of combined arms and rejected the American doctrine that held that tanks were for exploitation, not for fighting other tanks. He pressed American industry to produce more powerful engines and, often against the views of his superiors, pushed the development of the M4 Sherman, a medium tank with a 75mm gun. Not satisfied with the Sherman, he called for still more heavily-armed and -armored tanks. He wanted 250 of the new M26 Pershing tanks for Operation Overlord but was overruled. In May 1943, Devers became European Theater of Operations, United States Army (ETOUSA) commander. His principal tasks were overseeing preparation of detailed plans and the buildup of men and materiel for Overlord, and supporting the Combined Bomber Offensive. He clashed with General Dwight D. Eisenhower over the diversion of ETOUSA resources to Eisenhower's North African Theater of Operations. Eisenhower succeeded him at ETOUSA in January 1944, and Devers went to the Mediterranean as Commander North African Theater of Operations, United States Army (NATOUSA), and Deputy Supreme Allied Commander, Mediterranean Theater, to British General Sir Henry Maitland Wilson. Devers was involved in