First Siege of Callao
1821 CE.
Shown on the map at -12.033°, -77.133°.
The first siege of Callao was a prolonged military blockade of the Real Felipe Fortress (as well as other fortresses) in Callao by the Liberating Expedition of Peru under the command of General José de San Martín in July 1821 which culminated in the capitulation of Marshal José de La Mar in September of the same year, with him switching sides from the Royalist side to the Patriot side.
Text from the Wikipedia article First siege of Callao, licensed CC BY-SA 4.0.