Turkey, long Israel's best Muslim ally in a hostile Middle East, was highly critical of Israel's attack on Gaza 18 months ago, in which 1,400 Palestinians were killed.
Relations between the two states are now distinctly chilly and bloodshed at sea will do nothing to improve them.
The six-ship flotilla began the journey from international waters off the coast of Cyprus on Sunday afternoon after two days of delays. It had expected to reach Gaza, about 250 miles away, on Monday afternoon.
After nightfall Sunday, three Israeli navy missile boats left their base in Haifa, steaming out to sea to confront the activists' ships.
Two hours later, Israel Radio broadcast a recording of one of the missile boats warning the flotilla not to approach Gaza.
"If you ignore this order and enter the blockaded area, the Israeli navy will be forced to take all the necessary measures in order to enforce this blockade," the radio message continued.
Al-Jazeera earlier reported that the ships initially changed course to try to avoid a nighttime confrontation, preferring a daylight showdown for better publicity.
Read it all here.
While the aid flotilla was planned for months before the May 28-29 Rio meeting of the Alliance of Civilizations, it appears that Turkey and Spain, the founding sponsors of that anti-Zionist organization, gained renewed confidence at the conference which was attended by a US delegation. The Alliance of Civilizations is a UN organization and now the UN must take up this incident in a Security Council meeting to save face.