Diocletian was a Roman Emperor from 284 to 305, during his reign the Roman Empire was very vast, it covered Europe, North Africa and parts of Asia. Because of the size of the Empire, it was very hard to be ruled effectively and the creation of provinces made this harder.
Because of that, Diocletian decided to break the Roman Empire into two parts, one the Western Empire that had its capital in Rome and the Eastern Empire that had its capital in Byzantium. The Empire would have two Emperors that were in charge of each piece that would rule separately.
Germany's resumption of submarine attacks on passenger and merchant ships in 1917 became the primary motivation behind Wilson's decision to lead the United States into World War I.
