Mainland invasion of the United States

The concept of a mainland invasion of the United States relates to military theory and doctrine which address the feasibility and practicality of a foreign power attacking and successfully invading the contiguous United States of America. United States territory has been physically invaded twice in its history - once during the War of 1812 and again during World War II when Imperial Japanese forces occupied certain islands of Alaska. During the Cold War, most of the U.S. military strategy was geared towards repelling an attack on the United States by the Soviet Union.

The military history of the United States began with a foreign power on U.S. soil, the British Army during the American Revolutionary War. Following American independence, the next occurrence of an attack on American soil was during the War of 1812, also with Britain, and also the first and only time since the end of the Revolutionary War in which a foreign power occupied the American capital (the then capital city of Philadelphia was also occupied by the British during the Revolution).

The American Civil War may be seen as an invasion of home territory to some extent, with both the Confederate and Union armies each making forays into the other side's home territory. After the Civil War, the threat of an invasion from a foreign power was small, and it was not until the 20th century that any real military strategy was developed to address the possibility of an attack on America.

On March 9, 1916, Mexican revolutionary Pancho Villa and his Villistas invaded Columbus, New Mexico in the Border War's Battle of Columbus, triggering the Pancho Villa Expedition in response, led by Major General John J. Pershing.

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