Filibustering in Nicaragua In this image of a pitched battle in Nicaragua in 1856, Costa Ricans on foot fight American filibusters on horseback. Costa Rican soldiers and their Central American allies defeated William Walker’s filibusteros in 1857. The Pierce administration had already extended diplomatic recognition to Walker’s regime, and white Southerners had cheered Walker’s attempt to “introduce civilization” in Nicaragua and to develop its resources “with slave labor.” London Illustrated Times, May 24, 1856.