Pacocha exposed the limits of gunboat diplomacy

The Battle of Pacocha pitted Huáscar, then held by Peruvian rebels, against HMS Shah and HMS Amethyst with support from two Peruvian gunboats. Shah was an iron-hulled but wooden-sheathed unarmoured frigate, while Amethyst was a wooden screw corvette. The account links Shah to Edward Reed and notes that she had only been completed in 1875, so the mismatch could not be dismissed as a difference in age. The Royal Navy attempted a self-propelled torpedo attack, but it failed. Captain Algernon Horsey's force could not press two unarmoured ships decisively against the monitor, and the British withdrew. The embarrassment prompted questions in Parliament about why an armoured vessel such as HMS Warrior had not been available. Pacocha marked a technological limit on the traditional threat of British gunboat diplomacy.