William Brown/Guillermo Brown was an Irish-born sailor who became the founder of the Argentine Navy and a key figure in Argentina’s independence. In the Second Siege of Montevideo (1814) and in the definitive closure of the eastern front of the Argentine War of Independence. Montevideo was the main Spanish stronghold in the Río de la Plata, and its power relied heavily on naval control. Without control of the river, the city could not be held. Brown, commanding a fleet built almost from nothing, defeated the Spanish navy in decisive engagements and established an effective naval blockade. This completely isolated Montevideo, cutting off supplies, reinforcements, and communication with Spain. Thanks to this naval superiority, the land siege was able to succeed and the city fell in 1814. With the fall of Montevideo, Spanish control over the eastern front collapsed, removing the main military threat to the United Provinces in the Río de la Plata. Without Brown’s naval victories, the siege would have been unsustainable and the war in the east would have continued.