[5][2] Ewing enlisted as a private in the First Company, Fourth Battalion of the Cumberland County Militia, serving from 10 August 1780 until the end of the war.

In the War of 1812 Ewing became a colonel in the Miami County militia which joined General Harrison in his relief expedition to Fort Wayne in 1812.

[10] Colonel Ewing served with the army in a detachment of spies under his brother-in-law, Captain William Griffith, who was a survivor of the Ford Dearborn Massacre.

[11][12] In the aftermath of the Battle of the Thames, Ewing helped to identify Tecumseh's body, whom he knew well from his days as a trader.

[5] In the spring of 1822 Ewing moved his family to Fort Wayne, Indiana, and built the city's first tavern, later known as Washington Hall, at the corner of Barr and Columbia streets.