The larger submarines transferred to Alexandria had been part of Far Eastern deterrence because they could threaten Japanese supply lines. Commerce attack forces an opponent to assign escorts to merchant shipping. Those escorts are then unavailable for battleships, amphibious operations or other missions. A navy that tries to cover both risks weaker forces in each role, giving submarines more chances against major units. Moving the boats west strengthened the Mediterranean campaign but weakened the force intended to complicate operations against Singapore.
Chapter · 28:11-29:50
Far East submarines and the escort dilemma
Redeploying larger Far East submarines to Alexandria shows how commerce raiding changed escort demand and wider fleet options.