The Qustion of Arab unity: Why Unity?

(1)
Episode 1 of 9
Why Unity?

Part 1

(11 min)

Part 2

(12 min)

(2)
in the homepage of the Al Jazeera's series, it asked:

With the fall of Iraq to American and Allied forces and the possibility of a showdown between Christianity and Islam, is the Arab World on the brink of an abyss if it does not fullfil the promise of Arab unity?

Arab unity has been a dream and a promise since the fall of the Ottoman Empire, so why has this dream not been fulfilled in the last 100 years? What is the history behind its rise and fall?