Battle of Platsburgh
Governor-General Prevost decided to send an invasion force South of the border to try to seize as much territory as possible along the Richelieu River. Discussion between the two sides had not resulted yet in a treaty and both were trying to gain the upper hand. Prevost managed to group a large force of British Regulars (freed by the end of the Napoleonic War) and a small naval fleet under the command of Admiral Downie.
On the US side, the defence was left to Brigadier General Macomb and Admiral Macdonough. Due to the numerical inferiority of their forces, it was decided not to march North, but instead to fall back and make a stand at Plattsburgh which they reinforced with bunkers and other earthworks. The work, however, proved to be too arduous due to the small size of the force and Macomb requested that Vermont(which had, until then, stayed neutral) send militiamen.
When Provost's forces arrived, the defences were still not fully completed but, thankfully for them, Provost decided to wait for the arrival of Downie's Fleet. This, however, proved to be only a short respite.
The first British ships to arrive were gunboats under Captain Pring, mere hours in advance of the rest1 and they spent the next few days preparing for the engagement. Early in the morning of 11 September, the fleet began bombarding the town. This also signaled the beginning of Provost's advance.2
While the naval battle managed to turn to the favour of the US ships, the British infantry attacking from the West easily broke through the undermanned defences at Salmon River and, after entering Plattsburgh, even managed to turn some of the captured guns on the US fleet.
The US commanders were forced to capitulate, although, owing to the performance of Admiral Macdonough, the surviving US ships were allowed to retire with dignity after surrendering their cannons.3
Governor-General Prevost then ordered the occupation of the town and that repairs be made to the fortifications in case of a counter-attack from US forces. As most inhabitants had fled before the battle, the soldiers faced no real resistance and simply took their quarters in abandoned houses.
New England's Woe
The invasion and occupation of part of the Northern US states had a terrible impact on the morale of citizens of the neighbouring states. New Englanders, already hit hard by the embargo and fearing that it might eventually make the local economy collapse, began to openly talk about secession.
The members of the Federalist Party (which controlled the New England states) met during an event known as the Hartford Convention in early November4. While some advocated outright independence, the majority decided to first try to resolve the situation by negotiating some concessions from the federal government. To this end, the Federalist Party sent out three envoys to discuss some amendments to the Constitution which would allow them to begin trading with Great Britain once more.5
Treaty of Ghent
With the British being in a better position to negotiate after their victories and territorial gains, the Treaty's territorial claims were settled as Uti possidetis6 which saw the District of Maine, the land along the Richelieu down to Lake Champlain and part of the Bay of Biloxi joined British North America. It also gave Great Britain the Oregon Territory, all the islands within the bay of Fundy and sole control of the Great Lakes7.
As a gesture of goodwill, Washington and the surrounding lands were returned. However, many historians consider this decision to have been driven less by good nature and more by pragmatism (being a small, and hard to defend, enclave in hostile territory).8
Maine becomes a British Province. As part of the various treaties that created it, the Mainers are guaranteed: "the safe and full enjoyment of their private property, and to be protected in the exercise of their usual occupations." 9 Oregon is added to the North-West territory. Some of the lands south of the Great Lakes (and bordering lands occupied by US settlers) are granted to Britain's Native allies. This territory was not to be a province but a British protectorate10. The importation of slaves to the USA is also abolished and slavery is to be phased out.11