On July 30 General Taylor was ordered, with the troops concentrated on the Sabine, to occupy, protect, and defend Texas as far as occupied by the Texan's, and to approach the Rio Grande, which was “claimed to be the boundary between the two countries” (Texas and Mexico), but to remain away from Mexican settlements and military posts. In August Taylor camped at Corpus Christi, on the Nueces. On August 23 he was informed that, if a large Mexican army should cross the Rio Grande, the President would regard that act as an invasion of the United States and the beginning of hostilities; and on August 30 he was instructed that an attempt to cross on the part of a large Mexican force should “be regarded in the same light,” and that in such case he should consider himself authorized, in his discretion, to defend Texas by crossing the Rio Grande himself, driving the Mexicans from their positions on either bank, and occupying Matamoras. Before receiving this instruction General Taylor reported to the War Department that there were no concentrations of Mexican troops on the Rio Grande, and no expectation of war; he could hear only of small parties to be sent across the river by the Mexicans to prevent Indian depredations and illicit trade. On October 16, however, Taylor was again instructed to approach the Rio Grande, and to repel “any attempted invasion.” This instruction was crossed on its way by a despatch from Taylor, who had meanwhile begun to understand
