The squadron originally activated in the summer of 1917 as the Air Service 88th Aero Squadron and deployed to France during World War I to serve on the Western Front. The unit engaged in combat as a corps observation squadron with I, III, IV, and V Army Corps from May 30 to November 10, 1918. After the armistice, they subsequently served with VII Army Corps in occupation force from November 1918 to May 1919 when the squadron returned to the United States.
First redesignated as the 88th Squadron in 1921, they were assigned to Langley Field, Virginia. The unit participated in demonstrations of effectiveness of aerial bombardment on warships from 6 May to 3 October 1921. The squadron deployed for service in connection with civil disorders arising from West Virginia coal strikes in September 1922. Then, redesignated as the 88th Observation Squadron in January 1923, the squadron moved from Langley to support Army ground forces at Fort Campbell, Kentucky. The unit then moved to Brooks Field, Texas in 1927 to patrol the Mexican border, followed by Oklahoma in 1928 to support Fort Sill, then returned to Brooks Field in 1931.
The next assignment of station was to California in 1935 and was tasked to the new Hamilton Field near San Francisco as part of the 12th Observation Group flying the O-35 Douglas aircraft. The unit became a coastal patrol squadron, operating amphibian aircraft, and began to operate modern Martin B-10 bombers for the reconnaissance mission in 1936 when attached as the fourth squadron of the 7th Bombardment Group, 1st Wing, General Headquarters Air Force. The squadron dropped food and supplies and flew photographic missions in connection with flood-relief operations in central California, December 12-13, 1937. An upgrade of aircraft occurred to the B-18 Bolo in 1937 followed by early-model Boeing B-17C Flying Fortresses for long range reconnaissance patrols in 1939. A move to Fort Douglas, Utah in 1940 was required when the short runways at Hamilton Field proved inadequate for B-17 operations, with a secondary move to Salt Lake City Army Air Base in January 1941, where it was upgraded to the B-17E.
In early December 1941, the squadron was ordered to Clark Field, Philippines Commonwealth, to build up forces due to increased tensions between the United States and the Japanese Empire. Departure occurred on December 5, 1941 from Salt Lake City and December 6, 1941 from Hamilton Field bound for Hickam Field, Hawaii Territory. The air echelon came under attack during its arrival at Hickam on December 7, 1941. Some of the planes managed to land at Haleiwa Fighter Strip, one set down on a golf course, and the remainder landed at Hickam under the strafing of Japanese planes.
After the Pearl Harbor attack, the surviving aircraft operated from Hawaii until February 1942, becoming part of the air defense forces of the territory. The unit later moved to Australia with the 7th Bomb Group where the squadron reformed in northern Queensland in late February and became part of the new Fifth Air Force. They moved to Java, Dutch East Indies, in an attempt to stop the Japanese advance, however the small force of B-17s could do very little to stem the tide of the adversary. Launching valiant but futile attacks against the masses of the Japanese, they returned to the Royal Australian Air Force Townsville in early March 1942.
Redesignated as the 436th Bombardment Squadron in April 1942 and left its B-17Es in Australia, the squadron was reassigned to the new Tenth Air Force in India where it was re-equipped with long-range Consolidated B-24D Liberators. For the balance of the war, they carried out long distance heavy bomb raids over Japanese targets primarily in Burma, Thailand and Indochina. They also attacked Japanese targets in Southeastern China targeting airfields, fuel and supply dumps, locomotive works, railways, bridges, docks, warehouses, shipping, and troop concentrations in Burma and struck oil refineries in Thailand, power plants in China and enemy shipping in the Andaman Sea. (A more complete account is available in Lt Col (Ret) William Henderson's book, "From China Burma India to the River Kwai"). The unit ceased bombing operations in late May 1945 and was attached to Air Transport Command to haul gasoline from India over the Himalayas to China. The squadron demobilized in India, leaving B-24s to Indian Colonial forces, then deactivated as a paper unit in the United States in early 1946.
Reactivated in 1946 as a 7th Bombardment Group, they trained in global bombardment operations flying simulated bombing missions over various cities, as well as performing intercontinental training missions over the Pacific and later to Europe. In June 1948, the first Consolidated B-36A Peacekeeper was delivered and they operated B-36s until 1958 when the squadron began conversion to the B-52 Stratofortress.
In 1959, the unit was reassigned to Strategic Air Command (SAC) provisional 4238th Strategic Wing and reequipped with B-52F Stratofortress intercontinental heavy bombers at Barksdale Air Force Base, Louisiana to disperse its heavy bomber force. It conducted worldwide strategic bombardment training missions and provided a nuclear deterrent. The squadron was deactivated in 1963 when SAC deactivated its provisional strategic wings and redesignating them permanent Air Force wings. The unit was deactivated with aircraft/personnel/equipment being redesignated the 20th Bombardment Squadron in an in-place, name-only transfer.
The unit reactivated in 1986 as the 436th Strategic Training Squadron (STS) at Carswell AFB, Texas and supported the SAC mission through classroom instruction, multimedia production, and training aid fabrication. Due to a realignment of major commands in the Air Force in 1992, the 436 STS became the 436th Training Squadron as a Direct Reporting Unit under Air Combat Command. In 1993, the squadron was moved to Dyess AFB with the realignment of Carswell as a Joint Reserve Base.