James K. Polk
Message on War with Mexico
May 11, 1846

To the Senate and House of Representatives:

The existing state of the relations between the United States and Mexico renders it proper that I should bring the subject to the consideration of Congress. . . .

In my message at the commencement of the present session I informed you that upon the earnest appeal both of the Congress and convention of Texas I had ordered an efficient military force to take a position "between the Nueces and the Del Norte." This had become necessary to meet a threatened invasion of Texas by the Mexican forces, for which extensive military preparations had been made. The invasion was threatened solely because Texas had determined, in accordance with a solemn resolution of the Congress of the United States, to annex herself to our Union, and under these circumstances it was plainly our duty to extend our protection over her citizens and soil.

This force was concentrated at Corpus Christi, and remained thee until after I had received such information from Mexico as rendered it probable, if not certain, that the Mexican Government would refuse to receive our envoy.

Meantime Texas, by the final action of our Congress, had become an integral part of our Union. The Congress of Texas, by its act of December 19, 1836, had declared the Rio del Norte to be the boundary of that Republic. Its jurisdiction had been extended and exercised beyond the Nueces. The country between that river and the Del Norte had been represented in the Congress and in the convention of Texas, had thus taken part in the act of annexation itself, and is now included within one of our Congressional districts. Our own Congress had, moreover, with great unanimity, by the act approved December 31, 1845, recognized the country beyond the Nueces as a part of our territory by including it within our own revenue system, and a revenue officer to reside within that district has been appointed by and with the advice and consent of the Senate. It became, therefore, of urgent necessity to provide for the defense of that portion of our country. Accordingly, on the 13th of January last instructions were issued to the general in command of these troops to occupy the left bank of the Del Norte. This river, which is the southwestern boundary of the State of Texas, is an exposed frontier.

The movement of the troops to the Del Norte was made by the commanding general under positive instructions to abstain from all aggressive acts toward Mexico or Mexican citizens and to regard the relations between that Republic and the United States as peaceful unless she should declare war or commit acts of hostility indicative of a state of war. . . .

The Mexican forces at Matamoras assumed a belligerent attitude, and on the 12th of April General Ampudia, then in command, notified General Taylor to break up his camp within twenty-four hours and to retire beyond the Nueces River, and in the event of his failure to comply with these demands announced that arms, and arms alone, must decide the question. But no open act of hostility was committed until the 24th of April. On that day General Arista, who had succeeded to the command of the Mexican forces, communicated to General Taylor that "he considered hostilities commenced and should prosecute them." A party of dragoons of 63 men and officers were on the same day dispatched from the American camp up the Rio del Norte, on its left bank, to ascertain whether the Mexican troops had crossed or were preparing to cross the river, "became engaged with a large body of these troops, and after a short affair, in which some 16 were killed and wounded, appear to have been surrounded and compelled to surrender.". . .

The cup of forbearance had been exhausted even before the recent information from the frontier of the Del Norte. But now, after reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil. She has proclaimed that hostilities have commenced, and that the two nations are now at war.

As war exists, and, notwithstanding all our efforts to avoid it, exists by the act of Mexico herself, we are called upon by every consideration of duty and patriotism to vindicate with decision the honor, the rights, and the interests of our country. . . .

In further vindication of our rights and defense of our territory, I invoke the prompt action of Congress to recognize the existence of the war, and to place at the disposition of the Executive the means of prosecuting the war with vigor, and thus hastening the restoration of peace. . . .