He was a major participant in the Rosebud campaign, and saw action in the Battle of the Rosebud. General George Crook and his officers, having retreated from the Rosebud, were hunting in the foothills of the Bighorns when Grouard, known to the Brulé as 'One-Who-Catches' and to the Hunkpapa as 'Standing Bear', was acting as guide. Between 9 and 10 in the morning of June 25, 1876 Crook's forces were in Goose Creek Valley when Grouard saw the smoke from Indian signal fires in the distance, which indicated that George Armstrong Custer's command was engaged with the enemy, outnumbered, and being badly pressed. The officers present used their field glasses but could make no sense of the smoke signals and laughed at the idea that a half-Indian could have such knowledge of their meaning. To prove that he was right, at noon Grouard mounted his horse and rode towards the signals, reaching the Little Bighorn, a distance of some seventy miles, at 11 pm on June 25. Here he discovered the bodies of the slain before being chased back to Goose Creek by hostiles, bringing the news of Custer's death to Crook.