1811: The Battle of Calderon Bridge ends in Spanish victory. The Mexican War of Independence had begun the previous year, but was only briefly not a guerrilla war; 6,000 Spanish troops defeated some 100,000 rebels, which led to the capture of the rebel leaders and the dispersal of the rebel army into bands of insurgents. Mexico would fight for 11 years, eventually becoming independent in 1821.
1944: The Battle of Monte Cassino begins. This four month struggle was the main attempt by the Allies to break through the Winter Line in Italy, an extremely strong defensive position embedded into mountains. Only after 75,000 casualties and the destruction of an ancient monastery because of the erroneous belief that the Germans were using it as an observation post did the Allies break through.