The US-Mexican war began April 25, 1846 and ended two years later with the signing of the Treaty of Guadalupe Hidalgo. It is frequently confused with the Texas Revolution (1835-1836), the Spanish American War (1898), and even border skirmishes with Mexican revolutionaries (between 1913-1916). This may be because of the overshadowing of the US-Mexican War by the American Civil War, which is considered a much larger and more protracted conflict.

The war is claimed to have been fought to defend the right of a free people (namely the citizens of the republic of Texas) to determine their own destiny (which coincidentally was to join the American Union of States. Ironically, both sides agree that It was the Mexican government's right to deny them.

Most Americans supported the war (around 75,000 men enlisted in volunteer regiments and thousands enlisted in the US army, but only a few outspoken Whig politicians were against it...