From there two companies of the 18th advanced 91 miles to the northwest, where on August 13, they established a third post, Fort C. F. Smith on the Bighorn River. Given the typically early and severe winters of the high plains, the middle of August was very late in the year to begin constructing forts, but Carrington's march had been slowed by having to transport a large mechanical "grass-cutting machine." With replacements and reinforcements, Carrington's total force did not much exceed 700, of whom 400 were located at Fort Kearny.