On 20 August 1891, a successful amphibious landing was made by the rebels at the Bay of Quintero, approx. 20 miles north of Valparaiso. The landings were “desperate and rash.” True. The landing went smoothly, without opposition. Once ashore, the Congressionalist army advanced south to Valparaiso. The rebel fleet, then, approached Valparaiso Harbour, where it was held off at the harbour entrance by fire from Fort Andes (Fortín Prat (Fort Prat)?. reference

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What is likely to prove a decisive battle was fought in view of Valparaiso on Friday, Saturday, and Sunday, Aug. 21, 22, and 23. The struggle commenced on the first-named day at the mouth of the Aconcagua, when the Government troops were repulsed by the Congressionalist forces. The fact is that the landing of 8000 men by the insurgents had taken Balmaceda and his generals by surprise. They, however, displayed great activity and took a strong position on the beach of Vina del'Mar, when, according to the latest news from New York, Balmaceda's troops were again compelled to retire before the onslaught of the insurgents. A telegram from Lima, on the other hand, states that Balmaceda come off victorious and repulsed the attack of the insurgent troops, but both reports lack confirmation. The general impression is that the war cannot, under any circumstances, last much longer.
Valparaiso, with 100,000 inhabitants, is situated on the coast of the South Pacific Ocean, on a crescent-shaped range of steep hills around the wide bay, intersected by deep ravines breaking the mass of buildings into many detached clusters; while the high plateau above, called the Cerro, is also covered with houses. Along the shore of the bay, on the beach, runs the Circular Road, which is the main street for business, with goodly warehouses, banks, offices, and public buildings; the forts and batteries on the hills, armed with heavy guns, command every landing-place of the inner harbour. At one extremity of the bay is Fort Callao, behind which lies the seaside village of Vina del Mar, five miles from the city across the bay.