In the autumn of 1863 Banks organized a number of expeditions to Texas, chiefly for the purpose of preventing the French in Mexico from aiding the Confederates, and secured possession of the region near the mouths of the Nueces and the Rio Grande.
The Red, the Brazos, the Colorado, the Guadalupe, and the Nueces rise on the E.
Alligators are found in the low coast region and are especially numerous in the Nueces river.
The western boundary claimed by the republic was the Rio Grande to its source and the meridian of longitude from that point to the forty-second parallel, although as a political division of Mexico its limits never extended farther west than the Nueces and the Medina.
The Mexican commander, Pedro de Ampudia, demanded Taylor's withdrawal beyond the Nueces within twenty-four hours.
Later in June Polk, who assumed that the Rio Grande rather than the Nueces was the south-western boundary of Texas, ordered him to take up a position at the mouth of the Sabine, or at some other point best suited for an advance to the former river.
The commander of the Mexican Army of the North, Ampudia, immediately summoned him to retire behind the Nueces under the threat of interpreting his advance as an invasion of Mexican territory.