The Battle of Baton Rouge was a battle in the American-Mexican War fought in November and December of 1839, and marked the first American victory in the conflict after a fall of losses in Texas and the retreat into Louisiana. The battle marked the first of several attempts by the Mexican Army under Juan Lupe Valdez to cross the Mississippi River, all to no avail. Fought between 27 November to 6 December, it was the longest sustained fighting until the Battle of Covenant three years later. Many historians consider Baton Rouge the first important turning point in the war, as the Mexicans withdrew after heavy casualties attempting to cross the river and the collapse of the two beachheads they initially established, and gave an important morale boost to the Americans while protecting the crucial Mississippi River as an economic transit line and for military supplies.
After losses in San Antonio and Sutton, the Texian Army was in almost total disarray in the fall of 1839 and the US Army's overwhelming defeat at Houston marked the beginning of a rapid, haphazard retreat towards New Orleans, where more soldiers were arriving. To General Valdez and Mexican leadership, the next few weeks were viewed as offering a chance to deliver a potentially backbreaking blow to their enemies and thus pursued the American army towards Louisiana, crossing into official American territory on November 10. Valdez's army hesitated briefly near Vermilionville to regroup and fortify supply lines from Mexico, which were now reliant on boat transport through Galveston. The 16 days spent shoring up for the coming thrust allowed American soldiers to retreat across the Mississippi and bought time for reinforcements to arrive via New Orleans and Mobile to settle in in a rough line of small groups of soldiers between New Orleans and the town of Baton Rouge.
Valdez's long-game strategy involved eventually seizing New Orleans, the most crucial port in the Southern United States, but sought to first cut off American access to the city via the Mississippi. Aware that the river was the lifeblood of the interior United States, preventing the flow of ship traffic along it would deal a significant blow both the American war cause and the wider economy. Santa Anna endorsed this "Valdez Plan," seeing it as the most efficient way to bring a quick and decisive end to the conflict. Valdez selected Baton Rouge, located strategically near New Orleans and the Mexican supply lines through Galveston, as the place where he would make his attack, feeling that marching through low-lying marshland straight to New Orleans would strain his army and his line of supply. On November 25, he made his move out towards Baton Rouge.