[Sidenote: The difficulty in the way of acceptance of the proposition.] The great difficulty in the way of the negotiations was the fear on the part of the Texans that, upon the signature of the Treaty by the Presidents of the two countries, and before its ratification by the respective Senates, as required by the respective Constitutions, the Mexicans would collect all their forces and make one supreme effort to reconquer Texas. The Texans wanted the {306} protection of the United States in this interim, and the embarrassing question for Mr. Tyler's Administration was whether the President of the United States had the constitutional power to extend it. Would not war, undertaken in defence of one foreign Power against another, be offensive war, in the sense of the Constitution of the United States, such war as Congress alone can authorize? Or, could Texas be considered a part of the United States from the moment that the two Presidents signed the Treaty of annexation, and before its ratification by the respective Senates, thus making war in her defence defensive war, such war as the President of the United States may, of his own power, undertake? [Sidenote: The demand of the Texans for protection in the interim.] About the middle of January, 1844, Mr. Van Zandt demanded of Mr. Upshur whether, in case the President of Texas should agree to the proposition of the President of the United States for annexation, the President of the United States would protect Texas, from the moment of this agreement between the two Presidents, against all foreign attack. Mr. Upshur seems to have been greatly perplexed by the question, for he made no reply. About the middle of February, the President of Texas caused the same question to be put to the United States agent in Texas, General Murphy. Murphy was a blunt, brave man, full of chivalry, but quite empty of constitutional and international law. He immediately returned an affirmative answer, whereupon President Houston sent a special envoy to Washington, armed with plenary power to conclude a treaty of annexation. Whether Secretary Upshur, and, of course, the President, knew of the promise which Murphy had made for his Government to Texas, before the sudden death of Mr. Upshur, on February 28th, has never been determined.