At no time during the campaign were supply lines to Britain interrupted; even during the "Bismarck" crisis, convoys sailed as usual, although with heavier escorts. In all, during the Atlantic Campaign only 10% of transatlantic convoys that sailed were attacked, and of those attacked only an average of 10% of the ships were lost. Overall, more than 99% of all ships sailing to and from the British Isles during World War II did so successfully.