Within months of the Battle of Tippecanoe, the United States declared war against Great Britain. This required the increased manning of the Regular Army.
The modern 4th Infantry Regiment was constituted 11 January 1812 in the Regular Army as the original 14th Infantry Regiment, and organized in March 1812 in Virginia, Maryland, Delaware, and Pennsylvania.
On 12 July, General Hull crossed with his command into Canada, and made camp at Sandwich (now Windsor), Canada, just on the Canadian border. The regiment remained inactive for the rest of the month and grew restless. Then the Fourth was given a mission of escorting some supplies into Camp Detroit, previous escorts having been surprised and routed. The Fourth Infantry undertook this duty enthusiastically, and although ambushed at Maguage, fourteen miles below Detroit, by a superior force of British, Canadians, and Indians, the American regulars captured the enemy's concealed breastworks, wounded Chief Tecumseh, and completely routed their opponents.
Before they could follow up on their success and complete
After remaining several months in Canada as prisoners of war, the officers and men were returned under parole to Boston and given furloughs until exchanged for British prisoners of war. Early in 1813 the exchange was effective and the regiment reassembled and recruited to strength. It fought at the second Battle of Lacolle Mills, Canada and at Plattsburgh in 1814.
Following the end of the War of 1812, and consistent with the reduction in force of the Regular Army, the original 4th Infantry Regiment was consolidated on May–October 1815 with the 9th and 13th Infantry (both constituted 11 January 1812), the 21st Infantry (constituted 26 June 1812), the 40th Infantry (constituted 29 January 1813), and the 46th Infantry (constituted 30 March 1814) to form the 5th Infantry Regiment. Thereafter separate lineage.
In the same time period the 14th Infantry Regiment was consolidated May–October 1815 with the 18th Infantry Regiment and 20th Infantry Regiment (both constituted 11 January 1812) and the 36th Infantry Regiment and 38th Infantry Regiment (both constituted 29 January 1813) to form the modern 4th Infantry Regiment. On 21 August 1816 unspecified 4th Infantry Regiment companies were redesignated as Companies A and B, 4th Infantry Regiment. These companies would later be instrumental in the reorganization of 4th Infantry Regiment from the original organizational model, which included a headquarters element and 13 lettered companies with no battalion organization, to one with the 13 lettered companies divided between two battalions. The original Companies A and B would become Headquarters and Headquarters Company 1st and Headquarters and Headquarters Company 2nd Battalion.