The annexation of Texas by the United States provoked the Mexican ambassador and relations between the two nations were severed. However, the president of Mexico, Jose Joaquin Herrera, wanted to negotiate with the United States because he knew his country did not have the resources for a war. Herrera also knew that the Mexican people would be outraged at the loss of Texas. During negotiations, Herrera and Polk disagreed on the boundaries of Texas. Mexico believed Texas ended at the Nueces River. Polk and Texans claimed that the Rio Grande was the western border of Texas. As the discussion continued, Polk sent General Zachary Taylor to approach the Rio Grande in June 1845 with the order that war would commence once Mexicans crossed the border.
