At 2 p.m. U.S. troops arrived at the waterhole of Palo Alto as Mexican troops spread out on the prairie and cut the road, seeking to prevent the Americans from lifting the siege imposed on their fort across the river from Matamoros, which had barely three days' provisions left. In front of this overlook lay part of the old Port Isabel-Matamoros road, and about 300 yards to the right Mexican troops blocked the way to the Rio Grande with cannon and 3,200 men drawn in a line across the prairie. General Arista deliberately chose this field to lure U.S. troops into charging his line, so his powerful cavalry could sweep around and crush them.