Second Battle of Rivas: Juan Santamaría burns down the hostel where William Walker's filibusters are holed up.

The Second Battle of Rivas occurred on 11 April 1856 between Costa Rican militia under General Juan Rafael Mora Porras and the Nicaraguan forces of American mercenary William Walker. The lesser known First Battle of Rivas took place on the 29 June 1855 between Walker's forces and the forces of the Chamorro government of Nicaragua.

Juan Santamaría Rodríguez was a drummer in the Costa Rican army, officially recognized as the national hero of his country for his actions in the 1856 Second Battle of Rivas, in the Filibuster War. He died in the battle carrying a torch he used to light the enemy stronghold on fire, securing a victory for Costa Rica against American mercenary William Walker and his forces. Thirty five years after his death, he began to be idolized and was used as a propaganda tool to inspire Costa Rican nationalism. A national holiday in Costa Rica, Juan Santamaría Day, is held annually on April 11 to commemorate his death.

William Walker was an American physician, lawyer, journalist, and mercenary. In the era of the expansion of the United States, driven by the doctrine of "manifest destiny", Walker organized unauthorized military expeditions into Mexico and Central America with the intention of establishing colonies. Such an enterprise was known at the time as "filibustering".

A filibuster, also known as a freebooter, is someone who engages in an unauthorized military expedition into a foreign country or territory to foster or support a political revolution or secession. The term is usually applied to United States American citizens who incited rebellions/insurrections across Latin America with its recently independent but unstable nations freed from royal control of the Kingdom of Spain and its Spanish Empire in the 1810s and 1820s. These occurred particularly in the mid-19th century, usually with the goal of establishing an American-loyal regime that could later be annexed into the North American Union as territories or free states, serving the interests of the United States. Probably the most notable example is the Filibuster War initiated by William Walker in the 1850s in Nicaragua and Central America.