So, why do you think were the Uighurs so successful in their conquests? Was it due to their great leaders, sheer luck in facing empires weakened by internal strife, or a combination of both?
Definitely a problem with their enemies when it came to their defeat of Persia, and their conquest of the Holy Land. Persia was still recovering from civil war at the time, and the fact that the Emir of the Afghan lands virtually invited the Uighurs as foreign mercenaries to try and help him take the throne (which sort of backfired) was a big factor in their initial successes. The conquest of Transoxania was definitely a result of great leadership, though; there's a reason that the Battle of Andijan is still studied today.