At the same time the relative proximity of three natural harbours, Peiraeus, Zea and Munychia, favoured the development of maritime commerce and of the sea power which formed the basis of Athenian hegemony.
As in his active career he had wrought organic changes in the ordering, direction and control of fleets, so by his historic studies, pursued after his retirement, he helped greatly to effect, if he did not exclusively initiate, an equally momentous change in the popular, and even the professional, way of regarding sea-power and its conditions.
In an unsuccessful war against the Croats (1322-26), from which Venice derived the sole advantage, the ban appears to have learned the value of sea-power; immediately afterwards he occupied the principality of Ilium and the Dalmatian littoral between Spalato and the river Narenta.
The atrophy of the Ottoman sea-power had left the archipelago at the mercy of the Greek war-brigs; piracy flourished; and it became essential in the interests of the commerce of all nations to make some power responsible for the policing of the narrow seas.
The commercial relations with the North cannot be regarded as an important element in the union of the Hanse towns, but the geographical position of the Scandinavian countries, especially that of Denmark, commanding the Sound which gives access to the Baltic, compelled a close attention to Scandinavian politics on the part of Lubeck and the League and thus by necessitating combined political action in defence of Hanseatic sea-power exercised a unifying influence.
