The subject of the annexation of Texas to the United States began to be spoken of and strongly urged by the Texans themselves, but the movement was wholly disapproved by the party in that country opposed to the extension of slavery, since by the agreement then existing, all new territory south of a certain line permitted slavery, while the States north of it abjured it. In spite of the opposition of the North, however, Texas was admitted into the American Union by an act ratified in Congress in March 1845. This act was regarded by the Mexicans as an act of aggression. As Texas was at the time wholly independent of Mexico, its right was undoubted to annex itself to another country; but on the part of the United States the act is scarcely to be justified according to the laws of honor and international good faith. It was at any rate approved only by one section of the country, the other regarding every additional step leading to a foreign war with a neighboring government hitherto friendly, with regret and displeasure. The party which favored the measure began to make preparations for hostile demonstrations with alacrity. The American Republic had now long been at peace. Prosperous, safe from enemies abroad, peaceful at home, with plenty of money in her treasury, her military schools training a small body of officers in the latest science of the art of war, she was in perfectly good condition to resist an attack, and had the cause been a popular one, every State in the Union would have offered with alacrity volunteer troops for the field. The correspondence between the two countries grew embittered, and as time went on more and more unfriendly. During the negotiation of the treaty for annexation, war was permitted to go on in Texas; the government of the United States protested. In the war of words which followed, the Mexicans made and unfortunately reiterated the declaration that they should consider the ratification of the treaty as equivalent to a declaration of war. During this period of agitation and irritation, the Mexicans went on with "Plans" and pronunciamentos. Herrera was President during 1844, during which short period Congress decreed the destruction of Santa Anna. Farías returned to the Republic from a voluntary exile abroad. General Paredes on his way to the north with an army to check the approach of United States forces _pronounced_ a revolution and "Plan" at San Luis, and returned to Mexico to enforce it. He was made President, and remained in office six months, giving way then to a pronunciamento against him which resulted in putting General Don Nicholas Bravo at the head of government. In all this confusion, hurrying to and fro to find a government, there was no true leader of affairs to dictate wise and moderate steps in such an emergency. Santa Anna, the military genius of the country, was ready to serve it in his own way, by placing himself at the head of an army.