In company with members of the 5th, 13th, 23d Companies and the marine and sailor detachment from the USS Connecticut, Gross participated in the attack on Fort Riviere, Haiti, 17 November 1915. Following a concentrated drive, several different detachments of marines gradually closed in on the old French bastion fort in an effort to cut off all avenues of retreat for the Caco bandits. Approaching a breach in the wall which was the only entrance to the fort, Gross was the second man to pass through the breach in the face of constant fire from the Cacos and, thereafter, for a 10-minute period, engaged the enemy in desperate hand-to-hand combat until the bastion was captured and Caco resistance neutralized.