 The estimate of how long it would take for the fleet to reach Singapore after the outbreak of hostilities varied . It had to include the time required to assemble the fleet , prepare and provision its ships , and then sally to Singapore . Initially , the estimate was 42 days , assuming reasonable advance warning . In 1938 , it was increased to 70 days , with 14 more for reprovisioning . It was further increased in June 1939 to 90 days plus 15 for reprovisioning , and finally , in September 1939 , to 180 days . 
