The Mexicans were equally prompt, and the first collisions occurred at Palo Alto and Resaca de la Palma, near the Rio Grande. General Taylor repulsed the enemy with little difficulty and but small loss, and, crossing the Rio Grande, advanced upon and captured Matamoras. Thus far the hostilities had proceeded when a formal declaration of war was made against Mexico by the United States. Clay and the Whigs strenuously opposed this action; but the administration party bore down all opposition. Volunteers now flocked, especially from the Southern States, to Taylor's standard; and in a few weeks he found himself at the head of a resolute though not very well disciplined force of nearly eight thousand men. Monterey, a fortified town of considerable importance, was held by about nine thousand Mexican troops. General Taylor's objective point was the City of Mexico. [Sidenote: Taylor's Campaign.] After an attack of three days, Monterey fell into his hands. Victory followed his army everywhere. Santa Anna, a crafty and able man, who had sat in the presidential chair of Mexico, was now in command of the Mexican army, and confronted Taylor at Huena Vista. His gallant attempt to stay the advance of the triumphant Americans, however, failed, for Taylor defeated him in what was perhaps the most brilliantly and hotly contested action of the war. Taylor's force at Buena Vista numbered about six thousand men, the larger part of them being but rudely disciplined soldiers. Santa Anna's command comprised at least twenty thousand Mexicans. It was at Buena Vista that the Lancers, the best body of troops in the Mexican army, were routed by the dashing onset of the American volunteers. [Sidenote: Victory at Vera Cruz.] [Sidenote: Scott Enters Mexico.] General Scott now appeared upon the scene to reap fresh victories, and to lend powerful aid, by his scientific skill and ripe military judgment, in bringing the war to a decisive issue. He was despatched with an army to attack Vera Cruz, the most important port and fort on the Mexican coast. His force numbered between eleven and twelve thousand men, and he was supported by Commodore Matthew Perry, who operated with a fleet in the Gulf. Vera Cruz fell after a vigorous bombardment and a brave defence. The Mexicans could no longer hold the fortress of San Juan D'Ulloa, which was speedily occupied by General Scott. The two victories of Buena Vista and Vera Cruz rendered the cause of the Mexicans hopeless. The fall of the capital was only a question of more or less delay. The resistance of the Mexicans was still obstinate, though always ineffectual. The troops of the United States won in succession the battles of Cerro Gordo, Cherubusco, El Molino del Rey and Chapultepec. Finally, on the 14th of September, 1847, the American army of six thousand, under Winfield Scott, entered the City of Mexico. This was one year and four months after war had been declared by Congress.