The protected cruiser could not defeat an armoured cruiser or capital ship on equal terms, but it could destroy unprotected cruisers and threaten stronger opponents enough to complicate their choices. That made it naturally useful for commerce protection rather than the cheaper unprotected cruiser's commerce-raiding role. Even a losing fight against an armoured cruiser might inflict enough damage to shape the stronger ship's decisions. In South America, weak inland roads and railways made coastal shipping decisive, so control of the sea could determine an entire war's logistics.
Notable Point · 8:47-10:46
The protected cruiser as a commerce-protection warship
Follow the argument that protected cruisers fit commerce defence and regional sea control better than battles against capital ships.