Question: The Königsberg fortifications were erected due to the vulnerability during which war of 1563-1721?
Sentence (from "Battle of Zanzibar"): The German cruiser SMS "Königsberg" , while taking on coal in the delta of the Rufiji River (German East Africa), learned that a British cruiser—HMS "Pegasus" , which had been part of the Royal Navy's Cape Squadron sent to counter "Königsberg"—had put in at Zanzibar for repairs.
Relevant evidence: No