Complex sentence: Under the treaty, the Byzantines also ceded an area between the Black Sea and Strandzha to Bulgaria and in exchange the Bulgarians released the captured Byzantine soldiers and civilians who were allegedly 120,000.
Split into simpler sentences: Under the treaty, the Byzantines also ceded an area between the Black Sea and Strandzha to Bulgaria. In exchange, the Bulgarians released the captured Byzantine soldiers and civilians, who were allegedly 120,000.