The fast-emerging split between Turkey and Iran has revived a centuries-old rivalry between the Ottomans and the Persians.
Once friends, Turkey and Iran are finding that their reactions to the Arab Spring revolutions are driving them apart and renewing an old regional rivalry.
One sign of the deepening divide was obvious from the attendee list for an international conference on Afghanistan security that opened today in Istanbul.
Every primary player is here: 14 regional nations, with the presidents of Afghanistan and Pakistan in attendance, as well as more than a dozen other countries, including the United States. But Iran had planned to send just its low-ranking deputy foreign minister, despite its long border with Afghanistan and claims of being a regional superpower.