How many Ruler-class escort carriers would justify giving up two Illustrious carriers?
Short answerAbout twenty, because only a large escort force could free fleet carriers and materially reshape the anti-submarine and Mediterranean campaigns.
NotesThe trade becomes attractive at a high threshold of about twenty escort carriers. Those ships could replace obsolete training and support carriers and cover anti-submarine work. Fleet carriers would then remain available for the Mediterranean, potentially preserving Courageous and changing the carrier force at Taranto. Their value lies in compounding effects across carrier availability, convoy war, and experienced German submarine personnel.