Keyes uses the authority of supreme command to cancel the scheduled departures of the submarines Otus and Proteus. Their retention gives Singapore six submarines and six torpedo boats for local defence. Four sloops can spend the months from April laying substantial minefields around the approaches. Japanese ships coming directly to Singapore would therefore meet a layered threat from mines, submarines, and small torpedo craft. These forces provide local sea denial while the major surface fleet remains concentrated elsewhere.
Notable Point · 22:06-22:58
Layer mines and keep submarines at Singapore
Retaining Otus and Proteus and laying mines from April would give Singapore a local defence of six submarines, six torpedo boats, and obstructed approaches.