During the War of 1812, Michigan Territory (effectively consisting of Detroit and the surrounding area) was surrendered after a nearly bloodless siege in 1812. An attempt to retake Detroit resulted in a severe American defeat in the River Raisin Massacre. This battle is still the bloodiest ever fought in the state and had the highest number of American casualties of any battle in the war. Ultimately, Michigan was recaptured by Americans in 1813 after the Battle of Lake Erie. An invasion of Canada which culminated in the Battle of the Thames was then launched from Michigan. The more northern areas were held by the British until the peace treaty restored the old boundaries. A number of forts, including Fort Wayne were built in Michigan during the 19th century out of fears of renewed fighting with Britain.