Battle of Monte Santiago

The naval Battle of Monte Santiago was a naval battle on 7–8 April 1827, between the Argentine Navy and Brazilian Imperial Navy, during the Cisplatine War. It was a decisive Brazilian victory, though the Brazilian Navy lost twice as many ships as the Argentine Navy. The battle is highlighted by Argentine historians as one of the most courageous and ferocious naval encounters in the country's history. On that day, Sgt. Mayor Francis Drummond (engaged to Admiral Brown's daughter Elisa) died on deck, firing his marooned ship's cannons instead of retreating.

The Argentine Navy had severe losses and Brazil gained naval supremacy in the Rio de la Plata.

The battle
While the Brazilian Navy had high seas vessels, with more firepower but lesser speed, the Argentine Navy relied on fast maneuvering ships. Some Argentine commanders believed that the lack of maneuvering of the Imperial vessels in shallow waters and the speed of their own ships could decide some engagements in their favor.

The Argentine commander was confident that, by using the surprise element, his more maneuverable ships could inflict damage and that he could escape before the Brazilian force could counterattack.

Unfortunately for him, he was unaware of the enemy's initial three-to-one advantage in terms of ships on the first day of battle (which escaled into a four-to-one advantage by the second day). Brown also underestimated the Brazilian fleet's ability to cut off any route of escaping in time. As a result, the battle was a two-day pouring of shells onto his men.

On the second day, the Brazilian vessel Paula opened fire at the brigantine Independencia. The Independencia (which had lesser firepower) lost its masts, and to prevent the ship from sinking, 12 cannons were thrown overboard. As a consequence Francis Drummond, its captain, was wounded by a sliver that cut his ear. At 4 pm Drummond had no powder left, and had already fired his supply of three thousand rounds. Drummond managed to use anchor chains as amunition. He ordered "abandon ship", but the crew fiercely refused his command. Then Drummond, in order to resupply amunition, sailed in a lifeboat to the flagship Republica. At that moment he was hit by a 24 lb cannonball that destroyed his pelvis and right leg and died.

Aftermath
The losses in this battle, along with the loss of the 25 de Mayo (Argentine major vessel) in the battle of Punta Lara-Quilmes (June 29–30, 1826), gave the Brazilian Navy control of the River Plate. The Argentine Navy was almost completely destroyed and Brazil achieved naval supremacy. Only raids against commerce could be undertaken by Argentine Navy, mostly from its Atlantic base at Carmen de Patagones, since they could not fight the medium and large ships of the Brazilian Navy. Montevideo and Colonia, the two largest cities in the Banda Oriental, remained under Brazilian control.

But the heavy losses sustained by the Brazilians during these battles discouraged them from extending the naval war into the interior rivers of Argentina or attempting a direct attack against Buenos Aires.

This situation continued until the Preliminary Peace Convention, by which Oriental Province became the independent nation of Uruguay.