While the Western Powers generally had better intelligence in Europe, in South America they had failed to appreciate the threat to their supply lines and the seduction of New Granada and Brazil into the Korsgaardian sphere of influence. Within days of the New Granada initiation of hostilities, it became apparent that Brazil too was waging war against the United Provinces of South America.
New Granada advanced primarily in the Winter of 1889-90 along the Pacific Coast of the UPSA, with the bulk of their attack being by sea. This was a surprise to most as New Granada had never been known as a naval power. Granted, the UPSA itself only had a modest navy though larger than New Granada prior to the war. Interestingly, both were outfitted mostly with British surplus ships, with one important exception. New Granada at the eleventh hour was 'leased' several Shark Boats from Mexico with 'volunteer' crews. Most nations in South America had relied on the British to keep the peace on the naval front, but with the Royal Navy otherwise preoccupied across the globe and the surpise success of the Shark Boat and their self propelled naval mines, Sharks, the navy of New Granada was able to gain superiority over the local naval forces of the UPSA.
The Brazilians had been sullen over the victories of the UPSA and the loss of Rio Grande do Sul for generations, thus in one sense it was no surprise when they leapt at the chance for revenge. The Brazilians launched a main campaign to invade Rio Grande do Sul and cut it off from UPSA support, which would also place them within striking distance of the UPSA capital. While this effort in itself supported Brazilian war aims, it also served to hold down the majority of the USPA's military on the Atlantic Coast, just when their troops were needed on the Pacific coast. The Brazilians also sent a small overland force to support the New Granada effort to seize the Atacama Desert for its vital nitrites, though this was by and large a sideshow for the main event in South America. The Brazilians who did not have the Shark Boats of Mexico was unable to control the coast, though they did manage to keep occupied the UPSA's Atlantic Navy. Again, the two fleets were primarily composed of British surplus, pitting older models of British ships against one another.