Belloc offers that the Crusades might have been successful had the Crusaders taken the inland cities stretching from Aleppo to Damascus.  Had they done so, they would have separated the Moslem east from the Moslem west and at the same time protected the access to Jerusalem as well as their holdings along the coast of what is today Israel and Lebanon.

Recall also the similarity to today's chaos in the Middle East – chaos perpetrated by the west.  This chaos has destroyed the pockets of unity developing within these Moslem / Arab countries – Iraq, Libya and now Syria.  Might this fomented chaos serve a similar purpose?

On to Belloc:

…all that was needed to crystallise the military situation and determine Moslem victory was unity of command on the Moslem side.

"Unity of command on the Moslem side" did not occur during the first several decades of occupation by Crusaders.  However, this was slowly changing, first with Zengi: