Complex sentence: In 871, Emperor Basil himself led an attack on Tephrike, but failed to take the city and withdrew, but in 872/3, the Domestic of the Schools Christopher led another campaign that scored a decisive victory against the Paulicians at the Battle of Bathys Ryax.
Split into simpler sentences: In 871, Emperor Basil himself led an attack on Tephrike, but failed to take the city and withdrew. In 872/3, the Domestic of the Schools Christopher led another campaign that scored a decisive victory against the Paulicians at the Battle of Bathys Ryax.