A coup d'état in Athens in November 1973 had made Brigadier General Dimitrios Ioannides leader of the junta. Rigidly anticommunist, Ioannides had served on Cyprus in the 1960s with the National Guard. His experiences convinced him that Makarios should be removed from office because of domestic leftist support and his visits to communist capitals. During the spring of 1974, Cypriot intelligence found evidence that EOKA B was planning a coup and was being supplied, controlled, and funded by the military government in Athens. EOKA B was banned, but its operations continued underground. Early in July, Makarios wrote to the president of Greece demanding that the remaining 650 Greek officers assigned to the National Guard be withdrawn. He also accused the junta of plotting against his life and against the government of Cyprus. Makarios sent his letter (which was released to the public) to the Greek president on July 2, 1974; the reply came thirteen days later, not in the form of a letter but in an order from Athens to the Cypriot National Guard to overthrow its commander in chief and take control of the island.
Makarios narrowly escaped death in the attack by the Greek-led National Guard. He fled the presidential palace and went to Paphos. A British helicopter took him the Sovereign Base Area at Akrotiri, from where he went to London. Several days later, Makarios addressed a meeting of the UN Security Council, where he was accepted as the legal president of the Republic of Cyprus.
In the meantime, the notorious EOKA terrorist Nicos Sampson was declared provisional president of the new government. It was obvious to Ankara that Athens was behind the coup, and major elements of the Turkish armed forces went on alert. Turkey had made similar moves in 1964 and 1967, but had not invaded. At the same time, Turkish prime minister Bülent Ecevit flew to London to elicit British aid in a joint effort in Cyprus, as called for in the 1959 Treaty of Guarantee, but the British were either unwilling or unprepared and declined to take action as a guarantor power. The United States took no action to bolster the Makarios government, but Joseph J. Sisco, Under Secretary of State for Political Affairs, went to London and the eastern Mediterranean to stave off the impending Turkish invasion and the war between Greece and Turkey that might follow. The Turks demanded removal of Nicos Sampson and the Greek officers from the National Guard and a binding guarantee of Cypriot independence. Sampson, of course, was expendable to the Athens regime, but Sisco could get an agreement only to reassign the 650 Greek officers.
As Sisco negotiated in Athens, Turkish invasion ships were already at sea. A last-minute reversal might have been possible had the Greeks made concessions, but they did not. The intervention began early on July 20, 1974. Three days later the Greek junta collapsed in Athens, Sampson resigned in Nicosia, and the threat of war between NATO allies was over, but the Turkish army was on Cyprus.