h
annexation was consummated, it became a sectional issue,--Southern Whigs
favoring annexation and Northern Democrats opposing it.

So strong was the protest against annexation, that the treaty could not
command the necessary two-thirds vote in the Senate. The matter was
disposed of by the passage of a joint resolution (March 1, 1845) which
required only a majority vote in both houses of Congress. President Polk
therefore took office with the mandate of the country and the decision
of both houses of the retiring Congress, in favor of annexation.

Mexico, in the meantime, had offered to recognize the independence of
Texas and to make peace with her if the Texas Congress would reject the
joint resolution, and refuse the proffered annexation. This the Texas
Congress refused, and with the passage, by that body, of an act
providing for annexation, the Mexican minister was withdrawn from
Washington, and Mexico began her preparations for war.

President Polk had taken office with the avowed intention of buying
California from Mexico. The rupture threatened to prevent him from
carrying this plan into effect. He therefore sent an unofficial
representative to Mexico in an effort to restore friendly relations.
Failing in that, he and his advisers determined upon war as the only
feasible method of obtaining California and of settling the diplomatic
tangle involved in the annexation of Texas.

4. _The Conquest of Mexico_

The Polk Administration made the Mexican War as a part of its
expansionist policy.

"Although that unfortunate country (Mexico) had officially notified the
United States that the annexation of Texas would be treated as a cause
of war, so constant were the internal quarrels in Mexico that open
hostilities would have been avoided had the conduct of the
Administration been more honorable. That was the opinion of Webster,
Clay, Calhoun, Benton, and Tyler.... Mexico was actually goaded on to
war. The principle of the manifest destiny of this country was invoked
as a reason for the attempt to add to our territory at the expense of
Mexico."[29]

After the annexation of Texas it became the duty of the United States to
defend that state against the threatened Mexican invasion.

Mexican troops had occupied the southern bank of the Rio Grande. General
Zachary Taylor with a small force, moved to a position on the Nueces
River. Between the two rivers lay a strip of territory the possession of
which was one of the so