Pacocha exposes the limits of unarmoured cruisers

The 1877 Battle of Pacocha followed the rebel-held Peruvian monitor Huascar's harassment of commerce near Callao, including the forcible boarding of British merchant ships. Built by Laird Brothers at Birkenhead in the mid-1860s, Huascar was a substantial but ordinary ironclad. HMS Shah and HMS Amethyst confronted her without armour-piercing ammunition. Together they fired 427 rounds and made about sixty hits, but Huascar's protection defeated them. The first combat use of a Whitehead torpedo also missed. Huascar escaped under darkness and surrendered to Peru's own squadron two days later. Rear Admiral Algernon de Horsey returned without victory despite an enormous expenditure of ammunition. The result helped force renewed Royal Navy attention onto guns and armour.