American military technology during World War II American military technologies developed during World War II became more advanced and specialized as the war progressed . The technologies produced ranged in complexity from relatively simple items such as small arms and armored vehicles , including tanks , to more complex items such as the atomic bomb . The latter , produced under the secretive Manhattan Project , proved to be an incredibly powerful weapon that revolutionized warfare and was used to end the war . Other technologies , such as the M4 Sherman tank , the M1 Garand and M1 Carbine , and the gas mask , were refinements on previously existing technologies . Tanks . The M4 Sherman became the standard American military tank in World War II . Due to lack of development before the war leading to inexperience in tank design , the first large scale production of a medium tank was the M3 Lee , built for the US and the British , a compromise design with the main weapon mounted in the hull . The M6 series was the first of the heavy tank s used during the war . This particular tank series weighed approximately 50 to 80 tons . While there were demand for heavy tanks by some elements within the US Army , opposing views held predominated . Only one US heavy tank was produced during the war and it only reached Europe in the final months . As well as the US Army it was used to equip other western Allies serving alongside their own designs . Over 50 , 000 tanks were produced during the time of the war . Tanks like these were used during combat in mainly North Africa . However , this tank was named “ Ronsons ” for it was easy to set on fire . Atomic bomb . On August 6 and 9 , 1945 , an atomic bomb was dropped on the Japanese cities of Hiroshima and Nagasaki instantly killing 120 , 000 people . Roughly 100 , 000 more people died of radiation poisoning in the following years . Six days after the dropping of the bomb on Nagasaki , the Japanese surrendered . The Manhattan Project was the leading collaborative scientific effort and the most secretive of the time . At first , several different labs had scientists working on smaller parts of the atom bomb , but they had no idea as to the magnitude of the project . Later , the project was moved to Los Alamos , New Mexico , led by renowned physicist J . Robert Oppenheimer . After the use of the bombs , American journalists traveled to the devastated areas and documented the horrors they saw . This raised moral concerns and the necessity of the attack . The motives of President Harry Truman , the United States Army Air Force ( USAAF ) , and the United States Navy came under suspicion , and the USAAF and Navy released statements that it was necessary in order to make Japan surrender . Small arms . There were many small arms variants produced for use by U . S . forces during the war . Under the Lend - Lease Program , other Allied forces also gained access to a plethora of US weaponry . Common small arms used by rifle companies during the war included : the M1 Garand , M1 Carbine , and the . 45 caliber pistol . Mortar teams had 60mm mortars and snipers were issued a scoped M1903 Springfield . Submachine guns were sometimes used in place of the M1 Garand if there were enough to “ go around ” . The US entered the war with the M1 Garand as its service rifle . However , due to its size and weight , it was not an ideal weapon for some specialist roles such as engineers , tank crew , radio operators etc . So the lighter and smaller M1 Carbine was introduced in mid - 1942 . A semi - automatic weapon it used different ammunition to the M1 rifle . The standard US submachinegun was the Thompson . Designed in 1919 it was a reliable weapon but expensive and not suited to mass production . Work on a cheaper , simpler alternative - along the lines of the British Sten or German MP40 - began in 1942 . The M3 submachine gun was introduced in 1944 but problems lingered and it never completely replaced the Thompson . All soldiers were equipped with hand grenades . Special units such as flamethrower teams , wire cutter teams , and 81mm mortar teams could be assigned to companies as well as medics joining a battalion . These teams usually consisted of anywhere from two to five people with special training using their weapon . Soldiers could carry a total of 16 US issued guns during battle . US developments of other technology . Early in the war , the British realised that while they had some technological advances , these required American assistance for production . The Tizard Mission was sent to the US with several of these key technologies . One , the cavity magnetron was a breakthrough for radar . The MIT Radiation Laboratory was formed to develop radar and this led to gun - laying and aircraft radar and the LORAN navigation system . Another was the proximity fuze which the US developed to production so that it could be incorporated into bombs and artillery shells . When used in anti - aircraft guns the effectiveness against aircraft was significantly increased .