In the War of 1812, Macomb commanded troops at Sackett’s Harbor, the capture of Fort George and the St. Lawrence campaign. In 1814, he became a brigadier general before defeating the British at Plattsburg, New York. The action in Plattsburg earned Macomb a brevet major general rank and a gold medal from Congress.
In 1821, now a colonel again, Macomb became the chief of engineers. He married his second wife, Harriet Balch Wilson in 1826. Two years later he became a major general, and was the senior officer and commanding general of the Army from 29 May 1828 to 25 June 1841.