Just a few miles off the Turkish shore lies the small Greek island of Kastellorizo, an Islands of about 5 square miles inhabited by about 500 Greeks. Looking at a map one can see that there are a number of small Greek islands ( Some not so small like Rhodes) that lie just off the Turkey shore, seemingly in Turkish territorial waters. This was brought to my attention by an excellent article by Jack Dulgarian in Global Security Review DEFENSE & SECURITY Entitled “Kastellorizo Is The Key To Turkish & Greek Ambitions In The Eastern Mediterranean”at
Kastellorizo is the Key to Turkish & Greek Ambitions in the Eastern Mediterranean
His conclusion and key points are as follows:
“Turkey can quickly seize Kastellorizo and her satellites without repercussions. Claims to the islands, unchallenged military defense, an unstable domestic economy, a robust military, and apathy from Western powers on the global stage are all significant factors that can push President Erdoğan into this operation.”
“Taking Kastellorizo could also be a final play by Turkish grand strategists to get Greece to renegotiate the defining principles of the 1923 Treaty of Lausanne, which resulted in a Greek EEZ(exclusive economic zone) in the Aegean and Turkey ceding Cyprus (an agreement that Turkey has already broken). If Greece remains unprepared, it will lose territory, Turkey will gain a stronger foothold in quasi-internationally recognized Greek waters, NATO will remain submissive to an ally gone rogue, and Erdoğan will emerge as the dominant player in Eastern Europe and the Middle East.”

To get the details of the dispute you need to tread the short concise article.
My addition to this article is more historical. First of all the Greeks inhabited the western shores of Turkey since the time of Homer, about the middle 2nd millennium and remained there until after the WWI, in which they are displaced from their homelands by the Turks, revitalized after being allied with Germany in WWI. The expansion (in modern parlance termed imperialism) of the Ottoman Empire gradually brought the entire Greek population of Western Turkey under Muslim Turkish (Ottoman) occupation. As Bernard Lewis in his excellent book, The Multiple Identities of the Middle East, notes over a million Greeks some of whom spoke only Turkish and a smaller number of Turks, living in Greece, who only spoke Greek were forcibly resettled in their nation, as prescribed by the 1923 Lausanne Protocol. Being a loser in the war and the aftermath involved that the Ottoman Empire being divided up, the Sultan deposed, and the “modern Middle East” was created. Very few Greeks remain in Turkey, mostly in Istanbul ( Constantinople) and a couple of Islands in the Turkish Straits.
Secondly, like its Iranian neighbor, Turkey is an irredentist state with a ruler intent on establishing as much of the old Ottoman Empire as possible. Since the Lausanne Treaty Turkey has invaded and seized sizable portion of Cyprus,( 1974) ejecting all the Greeks, and earlier with a bogus referendum in the Syrian province of Alexandretta , once mostly Arab speaking, in 1939; Now known as the Hatay Province.
The differences between the two are in their way of war. Iran is subtle, cunning, using guile and weaknesses of the opponent, carefully assessing the situation before committing their resources. The Turkish despot Tayyip Erdogan is molded in the Turkish fashion, brute strength, overpowering force and predilection to use force, oblivious to civilian casualties. The Turks bomb and bombard Kurdish villages in both Turkey and Iraq without regard to civilian casualties.
Both Iran and Turkey see themselves as carrying the torch of Islam, Shi’a variety from Iran and Sunnism in Turkey. The problem is that in both varieties Political Islam or Islamism as it is called is totalitarian and radical. Both ruling cliques have embedded inimical views of minorities, especially Jews and Christians. Erdogan has hitched himself to the Muslim Brotherhood, one of the more insidious varieties of Islamism, and sees his new Ottoman Empire reaching into Europe by way of his control of hundreds of mosques and by way of of his turkic ancestry ( not wholly true) into Central Asia. Left to their own devices a confrontation is likely but not for the foreseeable future.

The yellow area depicts Greek speaking areas in 1910. The Orange is also Greek speaking but different dialect. Image from Wikipedia.
The Bottom line is simple. If Turkey chooses to invade these Islands , the Greeks cannot repel it. The Europeans will shrug their shoulders and so will the USA. There will be denunciations from various diplomatic organizations and world bodies but nothing will be done. And Erdogan knows it. What is ultimate objective to “renegotiate the Lausanne agreement giving Turkey control over these Greek offshore Islands.
As UK PM Neville Chamberlain said so famously….” How horrible it is , that we should be digging trenches and trying on gas masks because of a quarrel in a far away country between people of whom we know nothing…” That basically will be the Western reaction.
The ramifications of doing nothing, however, will be severe as the Lausanne agreement created the Middle East national boundaries and the cry from many who feel cheated, including the Kurds, will be to undo the Lausanne to their advantage. Effect? Further turmoil.

Myself in middle with Turkish officers on Cyprus. I highly respect the Turkish officers but abhor their political leadership. Erdogan has euthanized the officer corps after the attempted coup d’etat in July 2016.