The United States declared war against the United Kingdom, including Skrælige, in June of 1812. At first, Skrælige avoided the impact of the war - New England was staunchly against the war, and Britain was not even enforcing a blockade on New England in order to help exploit internal tensions. Actual warfare was focused in Upper Canada, and expanded that winter into the American Northwest. The garrison of British troops in Fort Charles wasn't even at full strength, with many being stationed in Upper Canada where the British were more vulnerable.
This changed in the middle of the night on the 9th of August, 1813. American-aligned saboteurs lit fire to the Þing and central market in Skrælingborough in order to stage a distraction and allow a small American force to land to the west. Unusually dry weather meant that this "distraction" became a full blown inferno. By the time the fire was brought fully under control the next day, most of Skrælingborough within the walls (which themselves were badly damaged) was turned to rubble.
During all of this, the Americans were able to surround and conquer Newhope, and force the surrender of Fort Charles. Many Patriots, who were descended from New Englanders, were sympathetic to the US. This allowed the US invasion force to quickly secure Havant and Abenakiborough upstream, and exert control over the lower Siguan Valley.
Rows of "Amshacks" in the outer part of Georgeville, Skrælingborough
After the centre of Skrælingborough burned down, there were suddenly over a thousand people made homeless. The American occupation force organized an effort to build temporary housing in the outer districts. This housing would serve as shelter until the rubble in the centre of the city could be cleaned up, and rebuilding could be done. The end result was basically a row of shacks, known as either "Amshacks" or "Patriot Estates" depending on the level of sarcasm and euphemism desired.
The occupation of the lower Siguan Valley was swift, but this wasn't the case in the upper valley or the outer coastal areas. The upper Siguan Valley was filled with loyalists and their descendants, and were essentially faced with a rerun of the revolutionary war from three decades ago. They did not have the strength to fight off the American invasion, but sporadic resistance efforts made administration a major headache. The coastal and island areas, meanwhile, were not outright opposed to occupation in the same way, but continued to engage in smuggling throughout the New England and Maritime Canadian region. The remoteness of these settlements from the centre of Skrælige meant that American efforts to stop this were futile, especially with the low number of troops they had available.
The balance of power of the war changed in 1814. Emperor Napoleon of France had been forced to abdicate, bringing a truce that allowed the UK to dedicate more forces to North America. The British blockade extended northwards to now cover all of New England and occupied Skrælige. On the 11th of July, efforts to reoccupy Maine began when the Royal Navy took Moose Island. In September they led the "Penobscot Expedition" to retake Penobscot Bay and reestablish New Ireland, and by October Skrælige was surrounded. After taking heavy losses at sea, the American land forces surrendered on the 21st of October, 1814.
Reconstructed extension to the Þing building, 1815.
One of the first rebuilt sections of Skrælingborough along King Street, 1815.
A new marketplace next to the dockyard.
The widened Vinstrileið split to go around one of the surviving gate towers.
The rebuilding of Skrælingborough ramped up once the British were back in control. Parts of the grid within the old walls were reconfigured, and main roads were widened and paved where possible - there was no appetite for further demolition. Full reconstruction would take several years, if not a decade or two, but new construction initially focused around King Street in order to help merchants and increase commercial activity.
The Skrælige Metropolitan Fire Department was founded in 1814, as one of the first acts of the "reliberated" colony. The burning of Skrælingborough showed that the disorganized volunteer system of firefighting used previously was inadequate for fighting major fires. The first municipal fire station was built in the middle of Skrælingborough, and other stations would be built soon thereafter - first in other sections of the city, and then in further out towns as well. This system of professional government-run fire departments would later spread throughout all of Skrælige, but the Metropolitan Fire Department would remain the biggest one through today.