Complex sentence: This led to military weakness, which allowed for the Turks to regain much of their territory in Anatolia and within two decades Constantinople would, for the first time in its thousand year history as capital of the Byzantine Empire, be conquered by a foreign power.
Split into simpler sentences: This led to military weakness, allowing the Turks to regain much of their territory in Anatolia. Within two decades Constantinople would, for the first time in its thousand-year history as capital of the Byzantine Empire, be conquered by a foreign power.