Uruguay is maybe the Belgium of South America, having the great misfortune to lie on a geopolitical fault line, in this case between the Spanish and Portuguese Empires, or later their heirs, Argentina and Brazil. The small city of Colonia de Sacramento for example changed hands 12 times between 1680 and 1828, and even then was later conquered by Guissepe Garibaldi during the Uruguayan civil war. However, we are looking here at the events of 1776-7, whilst the British and Americans were fighting at Brooklyn Heights and Quebec.
The entrance to old Colonia de Sacramento
An earlier war (in 1763-5) had gone well for the Spanish, capturing Rio Grande (the present day Brazilian city), the fortress of Santa Tereza and several other key locations. Ever since the Portuguese had plotted their revenge. They assembled 6,000 men (against 1,450 Spanish in the area) and in February 1776 two Portuguese fleets arrived at the Spanish fortress of Rio Grande de São Pedro and opened fire. The Portuguese commanders were Robert MacDouall and Jorge Hardcastle, just two of many British, or British descended, officers in the Portuguese Navy. A Spanish fleet attempted to intervene but after an inconclusive naval battle withdrew, and the Portuguese invaders pressed on inland, forcing the Spanish out of the area. After 27 days of siege a force of 4 companies of grenadiers defeated a Spanish force of 8 companies at nearby Lagoa dos Patos (Duck Lake), also burring Spanish ships that could not escape against a strong head wind. Following this the fort surrendered.
Not Rio Grande de São Pedro, but Fort Santa Teresa, which is still standing open to visitors
Despite this apparent victory, the Portuguese had miscalculated badly. With Britain bogged down around the world Spain had little to fear, and the response was designed to be overwhelming. 9,000 men were assembled in Spain, with 6 front line warships, 8 frigates and about100 transports. As important, for once the Spanish put a capable commander in charge, Pedro Antonio de Cevallos, the Viceroy of the Río de la Plata (Argentina). He had local knowledge after winning several battles in the 1760s.
Pedro Antonio de Cevallos
The Spanish fleet arrived in South America in Feb 1777. They found MacDouall, but his much smaller fleet managed to escape, so they sailed for the island of Santa Catarina (site of the modern Brazilian city of Floionopolis). When the garrison saw the huge Spanish fleet they fled without firing a shot, so Cevallos sailed for his 2nd objective, recapturing Rio Grande de São Pedro. Here the Portuguese had a piece of luck, a storm so damaging the Spanish fleet that they had to go to Montevideo for repairs. Cevallos split his forces, personally taking all the artillery and 4,500 men by ship to Colonia del Sacramento to which he lay siege. Despite heavy rain they set up a mortar battery, an eight pounder battery firing heated shot and various other cannon. The Portuguese garrison of 1,000 men were already in dire straits after a Spanish blockade, and with little hope of relief they soon surrendered. Cevellos demolished the walls to prevent reoccupation, and sunk blockships in the harbour.
Meanwhile, the rest of his fleet, the heavier warships, he sent hunting for MacDouall´s squadron. MacDouall was too wily however, and even succeeded in picking off one of a reinforcing squadron just arrived from Spain, the San Agustin. This he added to his fleet under yet another Englishman, Arthur Philip.
Cevellos now sailed back to Rio Grande de São Pedro, joining forces with the Spanish garrison of Santa Tereza. But before he could capture it, he received word that peace had been declared.
Aftermath
In February 1777 the worsening military situation, and the accession of a new Spanish born queen (Maria 1), led to the Portuguese seeking peace, and signing the First Treaty of San Ildefonso. Spain returned the island of Santa Catarina to Portugal, and recognised Rio Grande de São Pedro as Portuguese territory, but kept Colonia del Sacramento, the Banda Oriental, and the Misiones Orientales. Except for the Misiones Orientales, a region near Paraguay, this more less remains the Brazilian/ Uruguayan border today.
Portugal had been disappointed by lack of British support, and so remained neutral when Spain and Britain declared war, leaving Spain free to concentrate on Florida, the Mediterranean and besieging Gibraltar, draining yet more British troops from North America.
Spanish Forces
Flag of the Regiment of Guadalajara
Naval
The Spanish invasion fleet consisted of the following....
(Poderoso, 70 guns, Santiago la América, 64, San Dámaso, 70, Septentrión, 70, Monarca, 70, and San José, 70), 9 frigates,Santa Ana, Santa Clara, Venus, Santa Floritina, Santa Tereza, Santa Margarita, Santa Rosa, Liebre,
The unfortunate San Agustin (74) was dispatched later intending to join the main fleet.
Army
Cevallhos's expedition from Spain included 8,600 infantry, 640 dragoons and 150 gunners, organised in four brigades.
A captain in the Lusitania dragoons 1776
The regiments were as follows;
Dragones de Lusitania
Regimiento de Toledo.1 batt
Regimiento de Murcia.1 batt
Regimiento de Hibernia.1 batt. Formed mainly of Irish mercenaries, the "Wild Geese". Cevallos left William Vaughn of the Hibernia Regiment in command of the garrison in Santa Catarina.
Regimiento de la Princesa.1 batt
Regimiento de Cordoba.2 batt
Regimiento de Galicia.
Regimiento de Zamora.2 batt
Regimiento de Guadalajara.1 batt, who later formed part of the garrison of Santa Teresa.
Regimiento de Saboya.1 batt
Regimiento de Sevilla, 2 batt
Voluntarios de Cataluna.1 batt
Companies of grenadiers
Portuguese Forces
The Portuguese forces were under the overall command of Lt. Gen. Joao Henrique Böhm, a Prussian mercenary. It is much harder to get information of them than the Spanish, in part possibly because the Portuguese relied much more on local, less well documented, militia. This print is from the museum at Fort Santa Teresa, showing "Portuguese colonial troops of the 18th century".
Macdouall's fleet consisted of four ships of the line, including the Sao Antonio, 62, and four frigates, including the Nossa Senhora do Pilar. under Arthur Philip
Hardcastles little fleet had only 2 corvettes 2 brigs and 2 zumacas.
Further reading
Wars of the Americas by David Manley
Guerras entre España y Portugal en la cuenca del Río de la Plata.By Santiago Gómez.
http://www.todoababor.es/articulos/esp-port.htm
The fort at Santa Tereza in Uruguay is open to the public. It is very well preserved and has an excellent museum, well worth a visit.