One Million Nights
While the Roman Empire crumbled, Britannia may have fallen under the sway of the barbarian Saxons. However, when Arthur became King, he united his people and fought off the coming hordes. Upon his death at the hands of Mordred, Britannia fell under the rule of several, lesser leaders. These warlords were men of great means; their advisors led them away from the warlike behaviours that would have lead to another Saxon invasion. Held together by their faith in the Old Gods of Rome, the warlords held Britannia in relative peace for centuries.
When the Vikings invaded Britannia, destroying the temples to Zeus and Apollo, they met strong resistance from the warlords of Britannia. In Wales, the warlord known as Dewi the Wise concocted an allience with Norway, providing them a staging point for their frequent invasions of Britannia, Ireland, and France. Vexed by incursions of the Vikings, the Holy Roman Empire supports France in an on again-off again war against Britannia. Under the leadership of Pope Boniface IX, the Holy Roman Empire now undertakes a Crusade to bring Britannia back into the empire and stamp out their heathen religion.
Meanwhile, Islam spreads throughout the Middle East; the Mamluk-Burji Sultans, rule in a loose confederation with the remains of the Golden Horde.