On the morning of September 18, Brown surprised the British defenders at the southern end of the portage trail connecting Lake George to Lake Champlain. Rapidly moving up the trail his men continued to surprise British defenders and capture artillery pieces until they reached the height of land just before Ticonderoga, where they occupied the "old French lines" (so named because it was there that a French defense improbably held against a much larger British army in the 1758 Battle of Carillon). On the way he rescued 100 American prisoners (thus increasing the size of his force) and captured nearly 300 British. His demand for the fort's surrender was refused, and for the next four days Brown's men and the fort exchanged cannon fire, to little effect. Since he had insufficient manpower to actually assault the fort, Brown then withdrew to Lake George, where he made an unsuccessful attempt to capture a storage depot on an island in the lake.