Constantius Chlorus
When in 305 the 20-year term of Diocletian and Maximian ended, both abdicated. Their "caesares", Galerius and Constantius Chlorus, were both raised to the rank of "augustus", and two new "caesares" were appointed: Maximinus Daza ("caesar" to Galerius) and Valerius Severus ("caesar" to Constantius). These four formed the second tetrarchy.