In February 1861, William W. Heartsill, future mayor of Marshall, enlisted as a private in Co. F, of Col. John S.Ford's 2nd Texas Cavalry at Marshall, Texas. From April 1861 until November 1862, Heartsill was in a detachment of Col. Ford's 2nd Texas Cavalry which occupied Camp Wood in SW Texas. His detachment rejoined Confederate forces in Arkansas where he was captured in 1863 at Arkansas Post. In April 1863, Heartsill was exchanged and placed in a makshift infantry company in Georgia. He deserted his temporary unit and made his way back to Texas.

In March 1864, Heartsill joined the 2nd Texas Infantry Brigade, T.S.T. in Tyler and was a guard of Union prisoners at Camp Ford.