He fought Seminole Indians in Florida, 1840–1841; participated in the Military Occupation of Texas, 1845–1846; and fought in the Mexican–American War, 1847–1848. Sibley was on frontier duty in Texas from 1850 to 1855. Sibley was a creative military man. In the 1850s, he invented the "Sibley tent", which was widely used by the Union Army during the American Civil War and for a short while afterward. The United Kingdom also adopted the design of the Sibley tent. He also invented the Sibley stove (also known as the Sibley tent stove), to heat the tent. The Army used tent stoves of this design into the early years of World War II.