When it became apparent that the Crusaders would not rest until they had control of the city , al - Afdal marched out from Cairo .
Was too late to rescue Jerusalem , which fell on July 15 , 1099 .
When it became apparent that the Crusaders would not rest until they had control of the city , al - Afdal marched out from Cairo , but was too late to rescue Jerusalem , which fell on July 15 , 1099 .