ORDER OF BATTLE // May 18, 1811
Battle of Las Piedras
Estimated force strength by side, with confidence labels per surviving record.
Forces engaged
2 sides catalogued · combined 2,080 estimated
Spain
1,004
Medium-confidence figure
United Provinces of the Rio de la Plata
1,076
Medium-confidence figure
Battle context
The Battle of Las Piedras, fought on May 18, 1811, was a decisive engagement in the Rio de la Plata war of independence. The revolutionary forces under José Gervasio Artigas defeated the Spanish force commanded by José Posadas, inflicting casualties that ranged between 100 and 500 on the Spanish side. The two forces were closely matched in size — Spain fielding 1,004 troops against the revolutionaries' 1,076 — making the outcome a meaningful demonstration that patriot forces could overcome organized Spanish resistance in the field. The victory strengthened the position of the United Provinces of the Rio de la Plata in the broader independence struggle and established Artigas as a significant military commander in the River Plate region.
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