Complex sentence: When the last effective Ashikaga shogun Yoshiteru was assassinated in 1565, an ambitious daimyo, Oda Nobunaga, took the advantage and installed Yoshiteru's brother Ashikaga Yoshiaki to be the 15th Ashikaga shogun.
Split into simpler sentences: When the last effective Ashikaga shogun Yoshiteru was assassinated in 1565. An ambitious daimyo, Oda Nobunaga, took the advantage and installed Yoshiteru's brother Ashikaga Yoshiaki to be the 15th Ashikaga shogun.