On 18 April 1864, US forces sent a train out from Camden, Arkansas to capture bushels of corn discovered west of the town. The train was under the command of Colonel John Williams and escorted by around 1,100 troops from the first black unit of the Union army, the First Kansas Colored Infantry, composed primarily of ex-slaves.
On the way back, the train was intercepted by around 3,600 Confederates. The first two attacks were fought off successfully, but after the third attack US forces retreated to Camden.
Captured black troops attempting to retreat were executed by the Confederates, in what became known as the Poison Spring Massacre.