A study of how the coast and commerce of the Viceroyalty of Peru, from Chile to Ecuador, was defended against foreign intruders from the time of Francis Drake (1579) to the early 18th-c. The Armada del Mar del Sur carried silver to Panama, but also patrolled coastlines, offered protection to ports, and challenged interlopers. The dimensions, traits and guns of its vessels are studied, and its reliance on local expertise, manpower, and private investment in place of support from the Spanish crown. On land the book studies the construction and arming of fortifications at Callao, Guayaquil, Trujillo, and Valdivia, private initiatives at Arica, Pisco and Paita, the creation of the paid Callao presidio, and the formation and training of local militias in Lima. These processes are set against royal refusals to tolerate lower silver shipments from Peru to Spain caused by higher defence costs, and the strengthening of a local, Peruvian identity through military self-reliance in defence of local and royal interests.