Complex sentence: During the final century of the Ashikaga shogunate the country descended into another, even more violent period of civil war which started in 1467 when the Ōnin War broke out over who would succeed the ruling shogun.
Split into simpler sentences: During the final century of the Ashikaga shogunate the country descended into another, even more violent period of civil war. This started in 1467 when the Ōnin War broke out over who would succeed the ruling shogun.