The army remained in camp near Corpus Christi several months. The information Taylor obtained here and reported to Washington indicated no threatening movement on the part of the Mexicans; but on October 4th he suggested that, if the United States government meant to insist on the Rio Grande as the boundary, it would gain an advantage by occupying points on that river. He therefore suggested an advance to Point Isabel and Laredo.[110] Meanwhile had come the attempt to renew diplomatic relations between the United States and Mexico, which ended in failure. January 13, 1846, when it was known in Washington that Slidell would probably not be received by the Mexican government, Taylor was ordered to advance to the Rio Grande.[111]
Up to the time of this movement the Mexican government had neglected the distinction in the validity of its claims to the territory east of the Rio Grande. It strenuously asserted the right of Mexico to the whole of Texas, whatever its limits might be, and declared that annexation would be tantamount to a declaration of war. From the Mexican point of view, Taylor invaded Mexico the moment he entered Texas. But when he advanced to the Rio Grande the distinction was finally made. April 12, 1846, he was warned by Ampudia, general in command of the Mexican forces at Matamoras, to retire in twenty-four hours—not beyond the Sabine, as one might have expected from the previous attitude of the Mexican government, but beyond the Nueces.[112]
A few days later occurred the first conflict. April 24th a party of dragoons sent out by Taylor was ambushed on the east side of the river by a large force of Mexicans, and after a skirmish, in which a number of men were killed and wounded, was captured.[113] The official report of this affair reached Washington the evening of Saturday, May 9th.[114] President Polk had already decided, in conformity with the judgment of all his cabinet except Bancroft, to send to Congress a message recommending a declaration of war. Now, in formulating the reasons for the declaration, he asserted that “Mexico has passed the boundary of the United States, has invaded our territory, and shed American blood upon the American soil,”[115] and with the unanimous concurrence of his cabinet he sent the message to Congress, Monday, May 11th.
On the same day a bill providing for the enlistment of fifty thousand soldiers and the appropriation of ten million dollars, the preamble to which re-echoed the President’s assertion that war existed by the act of Mexico itself, passed the House by a vote of 174 to 14.[116]
II
CONQUERING A PEACE (1846–1848)
It was only after Polk felt assured of the refusal to receive Slidell[117] that he assumed an attitude so aggressive as clearly to challenge war; and from that time forward it seems to have been his desire to carry the struggle just far enough to bring Mexico to the point of conceding a territorial indemnity on the terms which he had intended to offer through Slidell. In accordance with this policy he suggested, while the question of Slidell’s reception by the Paredes government was yet in suspense, that Slidell should be directed to go on board a United States vessel and wait for further instructions.[118] The object of this plan was evidently to be able to resume negotiations, as soon as Mexico had felt the pressure sufficiently, without the delays incident to a correspondence between the two capitals. The same considerations influenced, at a later stage of the war, the appointment of Trist.[119] To this method of pushing on the conflict, with the sword in one hand and the olive-branch in the other, Polk applied the peculiar designation of “conquering a peace.”
After the declaration of war by Congress, May 12, 1846, General Scott, the commander-in-chief of the United States Army, was appointed to command directly the forces that were to operate against Mexico. According to a plan of operations which appears to have originated with President Polk himself, but which was concurred in by Secretary of War Marcy and by General Scott, New Mexico and California, which Polk intended to claim by way of indemnity, and Chihuahua, were to be occupied and held; the United States forces were to be pushed toward the heart of Mexico in order to force the Mexicans to terms; and the naval forces in the Gulf and the Pacific were assigned specific duties in connection with the general scheme.[120]
The plan was in keeping with the main purpose of the war, and was, on the whole, well adapted to insure success. The northern provinces were far distant from the city of Mexico; the hold of the central government upon them was but slight; and, even if its available forces had been sufficiently strong and effective to send the troops needed to resist invasion, the difficulties of transportation would have been hard to overcome. Of course, similar difficulties were experienced in throwing the United States troops into the interior of northern Mexico; but such operations were far easier for a strong government with abundant resources than for one so ill established and so lacking in means as that of Herrera or Paredes. The population of the north Mexican provinces was sparse and unenergetic, and could not be relied on for its defence; the local governments were weak and inefficient; and in 1846 that of California was disastrously affected by dissensions between two rival leaders, José Castro and Pio Pico, representing respectively the northern district and the southern.[121] It was in the northern district, in the lower valley of the Sacramento River and near the bay of San Francisco, that the foreign population, including the Americans, was most numerous.
The plan for a campaign directed at the city of Mexico was gradually developed as the war went on. The impression of Polk and his advisers at first was that a vigorous invasion of Mexico would end the war, without the necessity of pushing it far into the interior; and, since operations on the coast in the summer were so dangerous, the attack was made first in the north. The resistance of the Mexicans was, however, more desperate and prolonged than was expected, and ultimately the change was made to the shorter and more direct line of advance by way of Vera Cruz.
