Complex sentence: In response, the enraged Janissaries invaded the palace, and Mesih was sent to negotiate with them, appeasing them by promising, among other things, that only members of the "devşirme" would become viziers.
Split into simpler sentences: In response, the enraged Janissaries invaded the palace, and Mesih was sent to negotiate with them. He was able to appease them by promising, among other things, that only members of the "devşirme" would become viziers.