Â« Return to Table of Contents. 251. Recruits for a regiment of cavalry were concentrated at Fort Riley, Kansas, in August, 1866. The work of organization was inaugurated by Major John W. Davidson, 2d Cavalry, on the 10th September, and completed by Colonel Smith, on the 22d December. The new regiment was first designated in orders as the Eighth Cavalry, but the figure eight subsequently gave place to the cabalistic numberâseven.