This force was concentrated at Corpus Christi, and remained there 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.  From this quarter invasion was threatened; upon it and in its immediate vicinity, in the judgment of high military experience, are the proper stations for the protecting forces of the Government.  In addition to this important consideration, several others occurred to induce this movement.  Among these are the facilities afforded by the ports at Brazos Santiago and the mouth of the Del Norte for the reception of supplies by sea, the stronger and more healthful military positions, the convenience for obtaining a ready and a more abundant supply of provisions, water, fuel, and forage, and the advantages which are afforded by the Del Norte in forwarding supplies to such posts as may be established in the interior and upon the Indian 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.  He was specially directed to protect private property and respect personal rights.

The Army moved from Corpus Christi on the 11th of March, and on the 28th of that month arrived on the left bank of the Del Norte opposite to Matamoras, where it encamped on a commanding position, which has since been strengthened by the erection of fieldworks.  A depot has also been established at Point Isabel, near the Brazos Santiago, 30 miles in rear of the encampment.  The selection of his position was necessarily confided to the judgment of the general in command.