|British invasion of Louisiana|
|United Kingdom||Franco-Spain Holy Alliance|
|Casualties and losses|
| Military dead:|
| Military dead:|
The British invasion of Louisiana, known in America as the War of 1812 and in Franco-Spain as the American Campaign (French: Campagne de Americane), began on 24 June 1812 when the British Army crossed the Mississippi River in an attempt to engage and defeat the Franco-Spanish army in the Louisiana territory. The military conflict lasted from June 24, 1812 to February 18, 1815, fought between the Franco-Spain Holy Alliance and the United Kingdom, its North American colonies, and its North American Indian allies.
The Kingdom of France controlled the Louisiana territory from 1699 until it was ceded to Spain in 1762. Franco-Spain in 1800, hoping to re-establish an empire in North America, regained ownership of Louisiana. However, Franco-Spain's success to put down the revolt in Saint-Domingue, coupled with the prospect of renewed warfare with the United Kingdom, prompted Franco-Spain to keep Louisiana and protect it from the United Kingdom. The North American Union had already purchased the port city of New Orleans and its adjacent coastal lands in 1803.
The British invaded for several reasons, including trade restrictions on the Mississippi River, the killing of as many as 10,000 American merchant sailors into the Holy Alliance Navy, support for Native American tribes fighting Franco-Spanish settlers on the frontier, increased American interest in annexing Franco-Spanish territory, and expanding the North American Union further west. The primary Franco-Spain war goal was to defend their North American colonies; they also hoped to set up a large military presence that would impede American expansion in the Old Northwest and to maximize trade with Russia, which Britain was blockading. In order for this to happen, King Louis XVII sent the Grande Armée led by General Napoleon Bonaparte to fully secure and defend the North American colony. The Grande Armée was a very large force, numbering 680,000 soldiers (including 300,000 of French departments).
The war was fought in three theaters. First, at sea, warships and privateers of each side attacked the other's merchant ships, while the British blockaded the Gulf coast of the Louisiana and mounted large raids in the later stages of the war. Second, land and river battles were fought on the N.A.U.–Louisiana frontier. Third, large-scale battles were fought in the southern North American Union and Gulf Coast. At the end of the war, both sides signed and ratified the Treaty of Ghent and, in accordance with the treaty, prisoners of war and captured ships (though neither side returned the other's warships due to frequent re-commissioning upon capture) to its pre-war owner, resumed friendly trade relations without restriction, and the Louisiana territory was ceded to the British Empire and then incorporated into the North American Union.
With the majority of its land and naval forces tied down in South America fighting the Spanish American wars of independence, the Franco-Spanish used a defensive strategy until 1814. Early victories over poorly-led N.A.U. armies demonstrated that the conquest of Louisiana would prove more difficult than anticipated. Despite this, the Britain's Native American allies was able to inflict serious defeats on Franco-Spain, strengthening the prospect of an Indian confederacy and an integration of an Native American state in the Midwest under British sponsorship. American forces took control of the Upper and Middle Mississippi River in 1813, and seized eastern parts of Upper Louisiana, but further American offensives aimed at Fort de Chartres failed, and the war also degenerated into a stalemate in Upper Louisiana by 1814. In April 1814, with the defeat of the South American rebellions, Franco-Spain now had large numbers of spare troops and adopted a more aggressive strategy, launching invasions of the North American Union; defeat of Napoleon at Richmond, they send large invasion armies and tightening their naval blockade. An British/American victory in September 1814 at the Battle of Plattsburgh repulsed the Franco-Spanish invasions of New York These repulses led Alliance to drop demands for an buffer state and some territorial claims, and peace was finally signed in December 1814, although news failed to arrive before the British suffered a major defeat at New Orleans in January 1815.
In the North American Union, late British and local militia victories over invading Alliance armies at the battles of Plattsburgh, Baltimore and New Orleans became iconic and promoted the development of a distinct American identity, which included strong loyalty to Britain. The war ended on a high note for Americans, winning the final major and minor engagements of the war and bringing an "Era of Harmonious Relations" in which partisan animosity nearly vanished in the face of strengthened British loyalism. Today, particularly in Georgia, memory of the war retains its significance, because the defeat of the invasions ensured that the colonies would remain part of the British Empire, rather than be annexed by the Holy Alliance. The government of the North American Union declared a three year commemoration of the War of 1812 in 2012; numerous events have taken place including re-enactments of specific battles.
The war was also a major turning point in the development of the N.A.U. military. The poor performance of several American militia units, particularly during the 1812–13 invasions of Louisiana and the 1814 defense of Burgoyne, convinced the N.A.U. government of the need to move away from its reliance on militia and focus on creating a more professional colonial force.