By the late 1930s, an intrastate pipeline system carried west Texas crude oil east to refineries and shipping points, and in 1940 Texas produced almost 37% of the domestic oil in the United States while leading the nation in natural gas production. After the U.S. entered World War II in December 1941, west Texas reserves and new pipelines in eastern Texas put the state in a pivotal position supplying a large share of U.S. energy during the war. As German submarines disrupted Atlantic and Gulf of Mexico shipping, a major task of the Petroleum Industry Council for National Defense, created in Nov. 1941 and later renamed the Petroleum Industry War Council, was to move Texas oil safely to the U.S. east coast. Shipping disruptions in 1942 led to construction of the Big Inch pipeline for crude oil and the Little Big Inch for refined oil byproducts. Petroleum and its byproducts, including gasoline, diesel fuel, lubricants, and fuel oil, were essential to the war effort, and the Texas petroleum industry was key to Allied victory while foreshadowing major postwar growth in west Texas.