Israel and Greece have invoked the mutual defense pact they signed secretly only 12 days ago in the light of heavy Turkish sea and air movements in the eastern Mediterranean. 

DEBKAfile's sources report that this was decided in a long nocturnal phone conversation Wednesday night Sept. 14 between the Israeli and Greek prime ministers, Binyamin Netanyahu and George Papandreou, and at Israel's expanded cabinet of eight, which was called into session over the Turkish threat to its off-shore oil and gas rigs.
The Greek Prime Minister added to the information recorded so far on Turkish fleet movements in the Aegean and Mediterranean Seas. He was particularly concerned by the observation flights suddenly increased in the past 48 hours over the Greek island of Kastelorizo in the southeast Mediterranean just two kilometers from the Turkish coast. Those flights are escorted by Turkish combat jets.
Kastelorizo, Megisti and Ro Islands, on the underbelly of Turkey
Athens fears a Turkish attack on the island, whose population is fewer than 1,000, and an attempt to damage or seize it. Israel suspects that a Turkish attack on the Greek island will be the signal for Turkish military aggression against its oil and gas platforms located in the Mediterranean between Israel and Cyprus. Papandreou said the Turks are capable of surprise attacks on additional Greek islands near the Turkish coast.
Ankara would be acting on the pretext that Israel and Cyprus have no right to mark out and exploit the gas and oil zones of the eastern Mediterranean – a fuel-rich region known as Block 12 – without the consent of Turkish Cyprus (the Turkish Republic of North Cyprus – TRNC). Turkey also backs Lebanon's complaint that Israel is robbing it of its natural resources. Talks between Lebanon and Cyprus to resolve this issue broke down. Beirut refuses any discussion with Israel.
Neither Jerusalem nor Athens has disclosed in what way they have invoked the new defense pact.
DEBKAfile's military sources surmise that in the first stage, Israeli navy and air forces are to be posted at Greek Mediterranean bases. The two intelligence agencies are already sharing input.
Up until now, Israel could only respond to a Turkish threat from its own borders. With a presence at Greek military bases, Israel will be able to operate from the rear of Turkish forces in the event of an attack by those forces in the Mediterranean.

Monday, Sept. 12, Ankara dictated conditions for Israel to obey in order to keep its navy afloat free of Turkish aggression:
1. Israel vessels are prohibited from taking action against Turkish ships heading for the Gaza Strip. Prime Minister Tayyip Erdogan has declared "null and void" the UN report confirming the legality of Israel's blockade of Gaza.
2. Israeli warships crossing the 12-mile line bounding its territorial waters will be challenged by Turkish warships, which are instructed to approach them to within 100 meters and "disable their weapons."
This threat covers not only shipping bound for Gaza but also Israel's oil and gas drilling platforms which are more than 60 miles out to sea.
Israel's political and military spokesmen have been trying hard to downplay the Turkish menace. On Wednesday, Sept. 14, they brushed aside reports of Turkish naval and air movements in the eastern Mediterranean. After the cabinet of eight's meeting, the official line was that Israel is practicing "restraint in contrast to Turkish wildness" and they should be given time to cool down. In any case, the US and NATO were closely monitoring the crisis Ankara is generating with Israel, Greece and Cyprus, and won't let it degenerate into Turkish military action.   
But both Israel and Greece appear to know better: They decided to invoke their mutual defense pact – not before obtaining a green light from Washington – because they believe the Turkish threats indicated by its military movements are real and tangible.