Complex sentence: In 1947, when Gugsa Araya Selassie died, eastern Tigre was incorporated into western Tigre and was governed by Seyum Mangasha rather than by his dishonored son, who was not freed from his house arrest until after the Derg toppled the Ethiopian monarchy in 1974.
Split into simpler sentences: In 1947, when Gugsa Araya Selassie died, eastern Tigre was incorporated into western Tigre and was governed by Seyum Mangasha rather than by the dishonored Haile Selassi Gugsa. Haile Selassie Gugsa was not freed from his house arrest until after the Derge toppled the Ethiopian monarchy in 1974.