Military history of USA covers two century during which period USA emerged as new strong nation. The turbulent time was marked by War with Great Britain for independence (1775-1783), the great American Civil War (1861-1865) and finally World War II (1941-45) which saw USA to emerge as the sole super power of the late 20th Century.
The military history of USA began in 1775. From its formation the US Army was essentially land-based, its responsibility being fighting land battles and military occupation. For meeting different needs, different wings of the army developed -- Engineering Corps for controlling river inside US, Continental Army to stop invading British Army. From 1947, the army started proliferating with Army Air Force having its independent entity. Army was under War Department till 1947 and under Defense Department thereafter. Ever since, US Army fought in many wars.