Complex sentence: Chronicles relate that the Chancas prepared themselves for years to conquer the imperial city of Cusco, but only on account of the great figure and strategy of Inca Pachacutec, the Inca Empire did not yield.
Split into simpler sentences: Chronicles relate that the Chancas prepared themselves for years to conquer the imperial city of Cusco. Only due to the great figure and strategy of Inca Pachacutec, the Inca Empire did not yield.