The Battle of the Masts was one of the most pivotal and disastrous naval battles in Byzantine history. Most of the 500 ships were destroyed in a day, and it proved the mettle of the Muslims on the seas. Emperor Constans II barely escaped by trading clothes with another man and being disguised as a commoner. What if he had died that day, either being captured by the Arab armies, crashing and sinking to the bottom of the ocean, or simply dying from wounds? How does this affect the First Fitna? Does Constantine IV assume the throne earlier than OTL? Could we see a civil war? How does the Rashidun caliphate take advantage? Does the Theme system still get implemented? How do the Slavs and Lombards take advantage?