It was deemed proper to issue this order, because soon after the President of Texas, in April, 1845, had issued his proclamation convening the Congress of that Republic for the purpose of submitting to that body the terms of annexation proposed by the United States the Government of Mexico made serious threats of invading the Texan territory.  These threats became more imposing as it became more apparent in the progress of the question that the people of Texas would decide in favor of accepting the terms of annexation, and finally they had assumed such a formidable character as induced both the Congress and convention of Texas to request that a military force should be sent by the United States into her territory for the purpose of protecting and defending her against the threatened invasion.  It would have been a violation of good faith toward the people of Texas to have refused to afford the aid which they desired against a threatened invasion to which they had been exposed by their free determination to annex themselves to our Union in compliance with the overture made to them by the joint resolution of our Congress.  Accordingly, a portion of the Army was ordered to advance into Texas.  Corpus Christi was the position selected by General Taylor.  He encamped at that place in August, 1845, and the Army remained in that position until the 11th of March, 1846, when it moved westward, and on the 28th of that month reached the east bank of the Rio Grande opposite to Matamoras.  This movement was made in pursuance of orders from the War Department, issued on the 13th of January, 1846.  Before these orders were issued the dispatch of our minister in Mexico transmitting the decision of the council of government of Mexico advising that he should not be received, and also the dispatch of our consul residing in the City of Mexico, the former bearing date on the 17th and the latter on the 18th of December, 1845, copies of both of which accompanied my message to Congress of the 11th of May last, were received at the Department of State.  These communications rendered it highly probable, if not absolutely certain, that our minister would not be received by the Government of General Herrera.  It was also well known that but little hope could be entertained of a different result from General Paredes in case the revolutionary movement which he was prosecuting should prove successful, as was highly probable.  The partisans of Paredes, as our minister in the dispatch referred to states, breathed the fiercest hostility against the United States, denounced the proposed negotiation as treason, and openly called upon the troops and the people to put down the Government of Herrera by force.  The reconquest of Texas and war with the United States were openly threatened.  These were the circumstances existing when it was deemed proper to order the Army under the command of General Taylor to advance to the western frontier of Texas and occupy a position on or near the Rio Grande.