 Complete the following phrase:  Jackson began his United States Army career as a second lieutet in Company K of the 1st U.S. Artillery Regiment, proceeding through Pennsylvania, down the Ohio and Mississippi Rivers to New Orleans, and from there the troops embarked for Point Isabel, Texas, and were sent to fight in the MexicanAmerican War from 1846 to 1848. Jacksons command was directed to report to General Taylor and proceed immediately via Matamoros and Camargo to Monterey and then to Saltillo. Prior to the Battle of Buena Vista, Lieutet Jacksons command was ordered to withdraw from General Taylors army and march to the mouth of the Rio Grande, where they would be transferred to Veracruz. He served at the Siege of Veracruz and the battles of Contreras, 