Complex sentence: It was a fierce struggle, in which the Spaniards had to deploy large forces against this rural population, there was much cruelty on both sides; it ended with the death of the last Moorish leader in March 1571.
Split into simpler sentences: It was a fierce struggle, in which the Spaniards had to deploy large forces against this rural population. The revolt ended with the death of the last Moorish leader in March 1571.