Pretence for quarrel arose over the boundary between Texas and Mexico. The United States unjustly claimed that the Rio Grande was the southwestern boundary of Texas instead of the Nueces, as Mexico maintained. Mexico was invaded, her cities, including her ancient capital, were taken, and her badly-organized armies overthrown. Congress, by an Act of May 13, 1846, declared that "by the act of the Republic of Mexico a state of war existed between that government and the United States," and it virtually ended in September, 1847, though the final treaty of peace at Guadalupe Hidalgo was not signed until February 2, 1848. While the annexation of Texas was regarded by Mexico as a cause of war, yet she did not declare war on that ground. The principle of "manifest destiny" was proclaimed for the United States. In the prosecution of the war, with shameless effrontery it was justified on the necessity that "_we want room_" for the two hundred millions of inhabitants soon to be under our flag. Answering this cry, put up by Senator Cass of Michigan, Senator Thomas Corwin, in a spirit of prophecy, said: "But you still say you want _room_ for your people. This has been the plea of every robber-chief from Nimrod to the present hour. I dare say, when Tamerlane descended from his throne, built of seventy thousand human skulls, and marched his ferocious battalions to further slaughter,--I dare say he said, 'I want room.' Alexander, too, the mighty 'Macedonian Madman,' when he wandered with his Greeks to the plains of India, and fought a bloody battle on the very ground where recently England and the Sikhs engaged in a strife for 'room' . . . Sir, he made quite as much of that sort of history as you ever will. Mr. President, do you remember the last chapter in that history? It is soon read. Oh! I wish we could understand its moral. Ammon's son (so was Alexander named), after all his victories, died drunk in Babylon. The vast empire he conquered to 'get room' became the prey of the generals he trained; it was desparted, torn to pieces, and so ended. Sir, there is a very significant appendix; it is this: The descendants of the Greeks-- of Alexander's Greeks--are now governed by a descendant of Attilla." Through the greed of the slave power Texas was acquired, and they still longed for more slave territory, and weak Mexico alone could be depleted to obtain it. Southern California and New Mexico had a sufficiently warm climate for slavery to flourish in. The war was far from popular, though the pride of national patriotism supported it. Clay and Webster each opposed it, and each gave a son to it.(57) Abraham Lincoln, then for a single term in Congress, spoke against it, but, like most other members holding similar views, voted men, money, and supplies to carry it on. Senator Benton of Missouri, a party friend to the administration of Polk and favoring the war, said: