On the same day, a reconnoitring party of United States dragoons encountered a large detachment of Mexican soldiers, who had just crossed the river farther up, and were all killed or captured. General Taylor moved out from Fort Brown, opposite Matamoras, in order to cover his base of supplies at Point Isabel, and, having accomplished this, faced about again to relieve Fort Brown against assault from Matamoras. {330} While executing this movement he found himself, on May 8th, face to face with a Mexican army numbering three times as many men as his own. Nevertheless, he inflicted a crushing defeat upon the Mexicans in this battle of Palo Alto, and struck them again the next day at Resaca de la Palma, routing them completely, and driving the remnants of this once apparently formidable force across the Rio Grande. As soon as the news of these events reached Washington, the President informed Congress of them, claimed that war existed by the act of Mexican invasion, and asked for the means for its successful prosecution. [Sidenote: The attitude of Congress toward the war.] From the reception of this message to the end of the War, the Whigs in both Houses condemned the War, but only a few of them voted against furnishing the means for its prosecution. Strangely enough, they were aided by Mr. Calhoun, who opposed the whole war policy from the beginning to the end. He even opposed recognizing the existence of war. He was getting old and more peaceable in disposition, and also had probably seen, with Mr. Thompson, that any further slavery extension toward the Southwest meant the extinction of slavery in the border Commonwealths, and the greater exposure of the planting section to the influences of Abolition. Some of the Whigs claimed that if war existed at all, it was offensive war, and that the President had exceeded his constitutional powers in bringing it on, and should be impeached for so doing. The truth of this proposition depended, of course, upon the recognition by the United States of Mexico's title to the territory between the Rio Grande and the Nueces, or, at least, upon the recognition of it as a free zone, a proposition difficult to reconcile with the Acts {331} of Congress annexing Texas, and extending the revenue laws of the United States over this very district. The fact is, it was a defensive war at the outset, and if the Mexicans were excited to their move across the Rio Grande by the appearance of United States troops on the northern bank, they had only to thank themselves for bringing them there by previously massing their own troops on the south bank. [Sidenote: Congressional approval of the war.]