Battle of Fanfa
1836 CE.
Shown on the map at -29.915°, -51.548°.
The Battle of Fanfa, also known as Battle of Fanfa Island or the Betrayal of Fanfa, was one of the first battles of the Ragamuffin War, fought by loyalist Imperial forces under Bento Manuel Ribeiro, and Riograndense troops under Bento Gonçalves. It ended in a negotiated withdrawal for the rebel forces, who were meant to be allowed to leave the island unarmed, but in the end were imprisoned, including their leader Gonçalves.
Text from the Wikipedia article Battle of Fanfa, licensed CC BY-SA 4.0.