Early Arab Nationalism
From a 1915 Manifesto of the Arab Revolutionary Committee: "Arabs of the Christian and Jewish faith, join ranks with your Moslem brethren. Do not listen to those who say that they prefer the Turks without religion to Arabs of different beliefs; they are ignorant people who have no understanding of the vital interests of the [Arab] race."
Successes and failures of such cooperation occurred subsequently in the 20th century. Today's fight in Iraq and the Arab world more generally really is a question of whether broader visions of identity (as the early example above) will succeed, be followed on by models of political and economic power-sharing, and allow genuinely positive development to occur. Or if the rentier-state model married with the abuse of ethnic, religious and other prejudices (encouraged by the current rulers of the Americans, Israelis, Saudis, Jordanians, Egyptians, etc.) will be allowed to win out and ensure continued division and stagnation.