Cruiser Squadron

This is a List of squadrons and flotillas of the Royal Navy.

Starting around the time that steam cruisers became popular in the 1870s, the Royal Navy tended to organise such ships into groups called Cruiser Squadrons. Squadrons were commanded by a Rear-Admiral whose title was given as Flag Officer Cruiser Squadron n, or CSn for short (e.g. the officer commanding the 3rd Cruiser Squadron would be CS3).

During peace time the grouping was primarily for administrative purposes, but during war the whole squadron tended to be operated as a unified fighting unit and such units would train in this formation during peace. In the main fighting fleets (Home Fleet and Mediterranean Fleet) members of a given squadron were normally of the same or similar classes. The use of Cruiser Squadrons died out as the number of such ships decreased following World War II.

See Pennant number#Flotilla bands

...
Wikipedia