Given the need to run a convoy through the Mediterranean Sea, Admiral Cunningham proposed to stage a bombardment of Tripoli in conjunction with that operation. That seemed to satisfy the commanders in Britain. Captain Mack's destroyers had just destroyed a convoy off Sfax, so they were in a more accepting mood. The impending need to withdraw the troops from Greece was also a factor.
The harbour at Tripoli was about a mile square, and was enclosed by breakwaters. The town sits "on a rocky promontory which forms part of the western and northern perimeter of the harbour". The berths for ships are on the northern segment of the breakwater. A seaplane station was on the southeast corner. Admiral Cunningham's plan was to bombard at night, with flares dropped from aircraft from his aircraft carrier, which he did not want to risk in close to shore. This is based on the account in Vol.II of the Official History.