Elston started his military career as a Private in the War of 1812, a conflict between the U.S and Britain as a result of trade restrictions. He enlisted in 1814 and served a mere two weeks before he was discharged. This was when the Treaty of Ghent was signed, establishing no territorial loss for either side, and the war ended two months later.

Elston later earned his reputable military title as he served as a Major in the Black Hawk War of 1832. This was a brief conflict between the U.S. and Native American tribes including the Sauk, Meskwakis and Kickapoos. The conflict erupted after the Sauk war chief, Black Hawk, crossed the Mississippi River into Illinois with various tribes and attempted to resettle on tribal that had been ceded to the U.S. After several devastating battles, the tribes were eventually massacred while retreating to the Mississippi River.