John Slidell was an American politician, lawyer, slaveholder, and businessman. A native of New York, Slidell moved to Louisiana as a young man and became a Representative and Senator. He was one of two Confederate diplomats captured by the United States Navy from the British ship RMS Trent in 1861 and later released. He was the older brother of Alexander Slidell Mackenzie, a U.S. naval officer.

The Mexican–American War, also known in the United States as the Mexican War, and in Mexico as the United States intervention in Mexico, was an invasion of Mexico by the United States Army from 1846 to 1848. It followed the 1845 American annexation of Texas, which Mexico still considered its territory because Mexico refused to recognize the Treaties of Velasco, signed by President Antonio López de Santa Anna after he was captured by the Texian Army during the 1836 Texas Revolution. The Republic of Texas was de facto an independent country, but most of its Anglo-American citizens who had moved from the United States to Texas after 1822 wanted to be annexed by the United States.