The failure of Italy’s ‘parallel war’ was followed by turmoil caused by a combination of German intervention in the theatre and the British decision to send aid to Greece. The shift in focus towards what would be a disastrous Greek expedition resulted in neglect of the Axis sea lanes with North Africa, and abortive efforts at interdiction were made in the Adriatic instead. Yet, as this chapter shows, there were also positive developments in the campaign. New types of more suitable equipment and weaponry were employed, accompanied by the beginnings of a learning process to develop new tactics and procedures and to incorporate new technologies. This offered the potential for greater efficiency in anti-shipping operations, but it was only from April onwards that significant attention was again paid to them. Sinking rates promptly increased and, although the overall required Axis supply quotas were generally met, the losses did cause logistical pressure in certain key areas. While anti-shipping operations had been relatively limited in terms of quantity and effect over the first year of the war in the Mediterranean, an important foundation was laid in terms of recognition of their importance, increasing priority and operational learning. This provided the platform for what would be become a decisive campaign within the Mediterranean war.