Complex sentence: The Banner system the Manchus had relied upon so long failed: the Banner forces were unable to suppress the rebels, and the government called upon local officials in the provinces, who raised "New Armies" which successfully crushed the rebellion.
Split into simpler sentences: The Banner system the Manchus had relied upon so long proved a total failure, as the Banner forces were unable to suppress the rebels. The government called upon local officials in the provinces who raised "New Armies," which did prove a success in crushing the rebellion.