Sully’s route lay up the Cannon Ball River nearly to its source, and thence across to the head waters of Heart River. Here the General packed his train and left it with the emigrants under a strong guard, and himself and command, in light marching order, struck out for Knife River, where the Indians were reported encamped. He found them as expected. They were defiant and eager for battle, and an engagement immediately followed. The Indians were badly defeated, a large number being killed, and all of their property destroyed. This was the battle of Tahkahokuty, or Killdeer Mountain, and was fought July 28, 1864. [Sidenote: THE ARMY REACHES THE YELLOWSTONE.] Sully then returned to his camp on Heart River, and, under the guidance of a single Indian, who, of all those with him, professed to know a passable route, started on the perilous undertaking of carrying a wagon train through the Bad Lands to the Yellowstone River. The route was west to the Little Missouri, where it turned sharply to the northwest and struck the Yellowstone about fifteen miles below the Brasseau Houses. This point was reached on the 12th of August, and fortunately the supply steamers were close at hand to relieve the necessities of the troops. This was the first expedition across the Bad Lands of North Dakota, and was accomplished at the cost of great labor and suffering. The command crossed the Yellowstone and then marched to the Missouri River opposite Fort Union. This stream was forded with much peril, and the troops then returned to Fort Rice along the north shore. Garrisons were left at Forts Union and Berthold, but the contemplated post on the Yellowstone could not be built, owing to the wrecking of one of the steamers with most of the material on board. Thus the military forces of the United States were advanced in permanent occupation to the mouth of the Yellowstone River. Only twice before had the uniform of the American soldier been so far up the Missouri--in 1805–06, when the Lewis and Clark expedition passed this point, and in 1825, when General Atkinson took his command to a point about a hundred miles farther up. Neither of these earlier visits contemplated permanent occupation. [Sidenote: SIGNS OF WEAKENING.]