The class emerged from an arms race that began with torpedo boats, led to torpedo-boat destroyers, and then produced ships designed to kill those destroyers. Ten 4-inch guns and a battery of 3-pounders suited that job, while two single 21-inch torpedo tubes provided another offensive option. Service alongside battle squadrons added a communications role similar to that of frigates in age-of-sail fleet actions. In a smoke-filled battle, a small cruiser outside the line could observe and repeat visual signals after wireless aerials failed or were shot away, sometimes by the blast of its own side's guns.
Chapter · 4:48-8:57
Why the Blonde class were destroyer killers
The Blonde-class scout cruisers served as destroyer killers, flotilla support ships, and visual signal repeaters. Reconnaissance was a secondary concern.