Why did Diocletian divide the Roman Empire?

In A.D. 284, Diocletian became emperor. He believed that the empire had grown too large and too complex for one ruler to handle. In the most significant reform, he divided the empire into 2 halfs. One was named Greek-speaking east and the other Latin-speaking west. He took the eastern half for himself and appointed a co-ruler named General Maximian for the western half.