The following story is from the book, Indian Wars, by Bill Yenne.
The Grattan Fight, or Grattan Massacre, was a battle that should not have happened. The incident began on August 18, 1854, just east of Fort Laramie at a time when the Brule Lakota were camped there waiting for their government annuities. High Forehead, a Minneconjou man camping with the Brule, shot a lame cow belonging to a group of emigrants passing through on the Oregon Trail. A complaint was filed with Lieutenant Hugh Fleming, the post commander at Fort Laramie. He was inclined to let the matter slide in order to maintain peaceful relations with the Indians. However, a capricious young recent West Point graduate, Lieutenant John Grattan, insisted that he lead a detachment to arrest the man who had show the cow. Fleming agreed, apparently with reluctance.
On August 18, Grattan took thirty men from Company G of the 6th Infantry Regiment to the camp of Brule leader Conquering Bear at nearby Ash Hollow. Grattan proceeded to parley with Conquering Bear through an interpreter who is variously described as drunk, malicious, or both. The Brule offered to exchange horses for the sick cow-a deal that Grattan should have accepted-but Conquering Bear would not surrender High Forehead.
The discussion turned to an argument and a shot was fired, possibly by accident. Conquering Bear was shot down even as he tried to stop the ensuing firefight. Greatly outnumbered, Grattan attempted to retreat to Fort Laramie, but his command was surrounded and decimated. Only one survivor made it to safety, and he soon died of his wounds.
Rather than retaliating, the U.S. Army declared that Grattan had exceeded his authority. An explosive situation was not allowed to escalate, but the seeds of distrust and future violence had been sewn.
The distrust ran both ways. In Washington, U.S. Secretary of War-and future Confederate President-Jefferson Davis eventually decided that allowing the Grattan Massacre to go unpunished sent the wrong message to the Sioux. In August 1855, a year after Grattan's death, the U.S. Army launched a show of force on the Oregon Trail that was designed to send the correct message.