Okay I'm gonna give you dates, instead of some lame paragraph...
The Roman Empire was founded in the year 753 BC and lived all they way until the year 476 AD which is where the west side fell...Some reasons include Barbarian Invasion, Political Problems, Poor trading with the east, etc.....
After the West Part fell, the east controlled the east part of Europe until the muslims came in around 7th century... After many years around the year 1299 AD the Ottoman empire was founded over the ruins of the Byzantine Empire (Eastern Roman Empire). Finally World war 1 ended in the year 1918 and the Ottoman Empire lost much of it's territory and ended up collapsing in the following years after the war in 1922...
Hope this helps :)