In 1943 she went on the hazardous "Lisbon run". American ships would not enter Irish waters;Burne, page 537 they brought Irish-bound cargoes to Lisbon. Ships like the Mary B. Mitchell had to collect them. Britain had declared the Bay of Biscay to be an "exclusion zone"; their objective was to prevent supplies from reaching Germany, in particular Japanese exports. However Britain needed foreign currency, which she could obtain by exporting coal to Portugal. 'Navicerts' were introduced. Ships with a navicert were permitted safe passage through allied lines. They were to follow the line of longitude at 12° west.Forde, (2000). The Long Watch, page ii. Allied convoys to Gibraltar were at least 20° west to avoid the range of German bombers. However, it was difficult for sailing ships to adhere to this straight line, particularly in the stormy conditions, common in the Bay of Biscay.
