In President Sam Houston's second term (1841–1844), Dr. Smith was Minister Plenipotentiary from the Republic of Texas to the United Kingdom of Great Britain and Ireland and France, residing in London and Paris, respectively. He also traveled to Rome on a diplomatic mission to Pope Gregory XVI. In Europe, Smith secured ratification of a treaty of amity and commerce between England and Texas and improved the Republic's relations with France, which had been ruffled by the so-called Pig War. On his return from Europe in 1845, Smith was appointed Secretary of State by President Anson Jones. With the possibility of annexation by the United States Smith worked to give the people of Texas a choice between remaining an independent republic and being annexed. To facilitate this, he negotiated a treaty, in which Mexico recognized the independence of Texas, won in 1836, and in return Texas would not be annexed by another country. This treaty, known as the Cuevas-Smith treaty, angered many Texans who were strong supporters of annexation, and Smith was burned in effigy by citizens of Galveston and San Felipe. This treaty was rejected by the Texan Congress which preferred the annexation resolutions, and thus, Texas was annexed by the United States on December 29, 1845, and became the 28th state of the Union in early 1846.