At the time when the annexation of Texas took place, Texas had been recognized as an independent power, both by the United States and by several of the principal European powers; but its independence had not been recognized by Mexico, and the two contending parties continued to be at war. Under those circumstances, there is not the slightest doubt that the annexation of Texas was tantamount to a declaration of war against Mexico. Nothing can be more clear and undeniable than that, whenever two nations are at war, if a third Power shall enter into a treaty of alliance, offensive and defensive, with either of the belligerents, and if such treaty is not contingent, and is to take effect immediately and pending the war, such treaty is a declaration of war against the other party. The causes of the war between the two belligerents do not alter the fact. Supposing that the third party, the interfering Power, should have concluded the treaty of alliance with that belligerent who was clearly engaged in a most just war, the treaty would not be the less a declaration of war against the other belligerent. If Great Britain and France were at war, and the United States were to enter into such a treaty with either, can there be the slightest doubt that this would be actual war against the other party? that it would be considered as such, and that it must have been intended for that purpose? If at this moment, either France or England were to make such a treaty with Mexico, thereby binding themselves to defend and protect it with all their forces against any other Power whatever, would not the United States instantaneously view such a treaty as a declaration of war, and act accordingly? But the annexation of Texas, by the United States, was even more than a treaty of offensive and defensive alliance. It embraced all the conditions and all the duties growing out of the alliance; and it imposed them forever. From the moment when Texas had been annexed, the United States became bound to protect and defend her, so far as her legitimate boundaries extended, against any invasion, or attack, on the part of Mexico: and they have uniformly acted accordingly. There is no impartial publicist that will not acknowledge the indubitable truth of these positions: it appears to me impossible, that they should be seriously denied by a single person. It appears that Mexico was at that time disposed to acknowledge the independence of Texas, but on the express condition, that it should not be annexed to the United States; and it has been suggested, that this was done under the influence of some European Powers. Whether this last assertion be true or not, is not known to me. But the condition was remarkable and offensive.