Turkey and Israel were until recently the closest of allies, their people and governments united in the sense of isolation and co-operation that comes from being democracies in the Middle East, both nations of ethnic outsiders surrounded by Arab states.
But the scene in Istanbul on Monday, as tens of thousands of furious Turks marched on the Israeli consulate and filled Taksim Square in a mass expression of outrage at the Israeli military's raid on the Turkish-organized Gaza relief flotilla, threatened to tear apart any remaining sense of allegiance.
While Prime Minister Recep Tayyip Erdogan, a former Islamist, has brought a more critical voice to the country's relations with Israel during the past few years, Monday's attack widened the anger to encompass the secular opposition and other quarters usually allied with Israel, observers said.
"Relations between Turkey and Israel have not been the best for a few years, but before it has divided people, with some Turks very much in favour of better relations," said Cengiz Candar, a prominent Istanbul journalist.
"But what happened on Monday morning has brought everyone together, secular and Islamic, all political parties and walks of life - it has done irreparable damage to the relationship."
In an indication of the raid's dreadful timing, Turkey was about to hold joint military exercises with Israel, as the two countries have maintained close military alliances despite growing political differences, and co-operated on a wide range of activities behind the scenes. The exercises were cancelled Monday.
The Turkish foreign ministry declared in a statement that the raid would have "irreversible consequences in our relations."
About 400 of the 581 aid workers on the Mavi Marmara, a ship with a large Turkish flag on its side, sponsored by a Turkish charity, that was the largest of the ships in the flotilla, were Turkish, making it likely that at least some of those killed were Turkish citizens.
The raid caused Mr. Erdogan to cut short his trip to South America and to recall the Israeli ambassador. He described the raid as an act of "inhuman state terror" - language that had never before been used to describe Israel's relationship with Turkey.
After strong language was used in the wake of the 2006 Israeli attack on Lebanon, which prompted an angry Turkish public response and a rejection of Israel by Mr. Erdogan, the fury quickly died down and relations were normalized.
Turkish-Israeli relations had remained close until 2006 under Mr. Erdogan, and in military and diplomatic spheres had stayed co-operative afterward. This time, the anger seems more universal.
Turkey still has strong business and tourism links with Israel. Hundreds of thousands of Israelis each year visit the beaches and cities of Turkey, considered a rare example of tolerance toward Jews among Islamic countries. Turkey's strictly secular culture allows alcohol sales and prohibits the wearing of the veil in public places.
And Turkey played a key role in mediating between Israel and Syria, a diplomatic function that withered only after 2006.
The collapse in relations with Turkey could have repercussions. Turkey holds a seat on the United Nations Security Council and has the second largest military force in NATO. On Monday night, Turkey called an emergency meeting of the Security Council.
Mr. Erdogan has pursued closer relations with neighbours Iran, Iraq and Syria recently, while pursuing a tighter bond with the European Union.
Turkey and Israel have trade relationships worth more than $2.5-billion a year, after signing a free-trade agreement in 2000, according to Turkey's State Statistics Institute. Turkish companies have major building and infrastructure contracts in Israel.
"It's possible for there to be a total rupture in Turkey-Israel relations," Alon Liel, a former senior official in Israel's foreign ministry responsible for Turkish relations, told Business Week on Monday. "This would be an unbelievable blow."
Doug Saunders