The Treaty of Fort Laramie is an agreement between the United States and the Oglala, Miniconjou, and Brulé bands of Lakota people, Yanktonai Dakota, and Arapaho Nation. The first Fort Laramie treaty, signed in 1851, had been a resounding failure. The United States had almost immediately violated it, with American miners and settlers immigrating into Indian territory. The United States Army had further broken the 1851 treaty when it initiated an armed invasion that resulted in the Grattan massacre in 1854, which sparked the first Sioux War. The 1868 treaty negotiations were thus initiated to replace the 1851 treaty, which had proven entirely ineffective.