Maxentius refrained from using the titles Augustus or Caesar at first and styled himself "princeps invictus" ("undefeated prince"), in the hope of obtaining recognition of his reign by the senior emperor Galerius. However, the latter refused to do so. Apart from his alleged antipathy towards Maxentius, Galerius probably wanted to deter others from following the examples of Constantine and Maxentius and declaring themselves emperors. Constantine firmly controlled his father's army and territories, and Galerius could pretend that his accession was part of the regular succession in the tetrarchy, but neither was the case with Maxentius: he would be the fifth emperor, and he had only few troops at his command. Galerius reckoned that it would be not too difficult to quell the usurpation, and early in 307, the Augustus Severus marched on Rome with a large army.