On August 27, Gálvez set out by land toward Fort Bute, leading a force that consisted of 520 regulars, of whom about two-thirds were recent recruits, 60 militiamen, 80 free blacks and mulattoes, and ten American volunteers headed by Oliver Pollock. As they marched upriver, the force grew by another 600 men, including Indians and Acadians. At its peak, the force numbered over 1,400, but this number was reduced due to the hardships of the march by several hundred before they reached the fort.