In March of the next year, Congress sanctioned the annexation of Texas, and trouble with Mexico began in earnest. History records the rapid course of events which made up the Mexican War. We can only notice the events which directly concern the career of Grant. His company was a part of the expeditionary force of three thousand men destined to see active service on the border. By the middle of March they had reached the Rio Grande, and pitched camp opposite the city of Matamoras. Their army was far from its base of supplies and in a country swarming with the enemy. Before war was formally declared, two officers who were caught outside the camp were killed, and two whole companies captured. There was no railroad, and General Taylor was compelled to send a considerable force back twenty-five miles for supplies. On the third of May the returning troops encountered a much larger force of Mexicans. A battle followed which continued after sundown. During the night the Mexicans retreated, but were found further on, in a much stronger position. They awaited the Americans on the far side of a pond, their position being further fortified by logs and branches of trees. The captain of Grant's company was temporarily absent, and it fell to Grant to lead their advance. By this time the bullets were humming merrily, but he directed his men to deploy to one side and approach through thicker woods. At last they reached a clearing near the head of the pond, and he ordered a charge. They captured the position immediately in front of them, and made a few prisoners, including one colonel. The engagement all along the line had been too brisk for the Mexicans, and they broke and ran, leaving a considerable quantity of guns and ammunition. As for the little lieutenant, it was his first battle, and first command of a company, and he had reason to feel satisfied with the day's work. As one result of the engagement, the Americans now crossed the river, and became an Army of Invasion. And now that war had actually begun, volunteers began to flock to the standard. The ensuing months of that year were packed with incident and no little danger. In August, Grant was made quartermaster and commissary of the regiment--a position of responsibility which he held until the army was withdrawn. Although Grant's duties were now such as to withdraw him from active fighting, he was not the man to take advantage of the fact. The lively battle at Monterey bears witness of this. After a hard encounter on the outskirts of the city, the Americans stormed it from the north and east, and began to drive the Mexicans out, street by street. But when the citadel was in sight, the commanding officer, Colonel Garland, found to his dismay that they were short of ammunition. "We must have ammunition at once," he announced to his men. "Who will volunteer to ride back with the message? I do not wish to detail any one, as it is extra hazardous."