What was the title given to the leader of Russia in the period before the revolution?

Vladimir Ilyich Ulyanov, better known by his alias Lenin

3, many invasions from the Ottoman Turks resulted in the rapid decline of the Byzantine empire, 450 AD to 1454 AD

4 Many plagues, brought over from the Turks erupted in citys like Athens and Constantinople, killing a good chunk of the Empire's population