He was graduated in 1843, and appointed brevet second lieutenant in the Fourth Regiment of Infantry. The engineers and the cavalry are considered more desirable arms of the service than the infantry, and the best scholars at the Military Academy are assigned to them. Grant's rank placed him in the latter. His regiment was sent to Jefferson Barracks, St. Louis. Frederick T. Dent, his classmate, was in the same command, and resided in the vicinity. He was invited to the house of the Dents, where he made the acquaintance of Miss Julia T. Dent, who became his wife five years later. In 1845, the events which led to the Mexican War assumed form, and Grant's regiment was ordered to Corpus Christi, where he was commissioned as a full second lieutenant. His post was situated at the mouth of the Rio Nueces, between which and the Rio Grande was a triangular section of territory claimed by both governments; and this was the nominal subject of dispute between the United States and Mexico. General Taylor, commanding about four thousand troops, was ordered to move his force to the Rio Grande, on which the Mexicans had concentrated an army. A body of United States dragoons, commanded by Captain Thornton, was surprised by an overwhelming force of the enemy, and all of them killed, wounded, or captured. This event fired the blood of the soldiers, as well as of the people of the country, and Taylor crossed the river with the main body of his little army. The Mexican generals declared that the advance of Taylor into the disputed territory was an act of war, and active hostilities had commenced. While the general was hastening to reinforce one of the forts attacked, he came upon the Mexicans drawn up in order of battle at Palo Alto. An action, mostly with artillery, followed, and the enemy were defeated and driven from the field. It was the first battle fought in thirty-one years with any foe other than Indians, by American soldiers. Grant was in that first conflict of half a century, as he was in the last ones. The Mexicans had fled from this first considerable battle of the war to Resaca de la Palma, where they had established themselves in a strong position. Taylor attacked them the next day, and though their force was triple that of their assailants, they were again defeated and routed. The Mexicans fought with dogged courage, however they may be judged from the events of the war. Three months later, General Taylor marched upon Monterey with an army reinforced to 6,000 men. It was strongly fortified, but the city was captured after a hard-fought battle.