Dodecanese relative quiet and prosperity. In 408 BC, the three cities of Rhodes had united to form one state, which built a new capital on the northern end of the island, also named "Rhodes"; this united Rhodes was to dominate the region for the coming millennia. Other islands in the Dodecanese also developed into significant economic and cultural centers; most notably, Kos served as the site of the school of medicine founded by Hippocrates. However, the Peloponnesian War had so weakened the entire Greek civilization's military strength that it lay open to invasion. In 357 BC, the islands were conquered by
Dodecanese sources in the 8th century, as a naval command under a "droungarios", encompassing the southern Aegean Sea, which eventually evolved into the Theme of Samos. However it was not applied to the current island group, but to the twelve Cyclades islands clustered around Delos. The name may indeed be of far earlier date, and modern historians suggest that a list of 12 islands given by Strabo ("Geographica" Χ.485) was the origin of the term. The term remained in use throughout the medieval period and was still used for the Cyclades in both colloquial usage and scholarly Greek-language literature until the