Good answers from my fellow respondents. So:
- For a long time, there was no Greece, so there was noone to do the holding on.
- For a long time after that, Greece didn’t have most of the islands: it had to get hold of them:
- The Cyclades and Euboea, and the Saronic Gulf islands, were part of the Greek state since 1832
- The Ionian islands were ceded to Greece in 1864
- Most of the islands of the Aegean were ceded in 1913
- The Dodecanese were ceded in 1946
Greece did not get all the islands either: the strategic islands of Imbros and Tenedos are now officially named Gökçeada and Bozcaada, because they remained part of Turkey. Their Greek population of the islands was not subject to the 1923 Population exchange between Greece and Turkey, but it has substantially diminished since. In fact, a fair proportion of them are my parents’ neighbours in Melbourne.