Their first choice was a man named Marcus whom they appointed emperor. After a short period, unhappy with his performance, they killed him and appointed Gratian. He also failed to meet the troops' expectations and was killed after four months. They next chose as their leader a man named after the famed emperor of the early fourth century, Constantine the Great, who had himself risen to power through a military coup in Britain. Flavius Claudius Constantinus was a common soldier and early in 407, possibly February, his fellows acclaimed him as emperor. Rebellion in Roman Britain was not unusual, a contemporary described it as a "province rich in usurpers". It was on the periphery of the Empire and there was a common view that it was overlooked in terms of resources and patronage. However, such revolts were usually short-lived; Constantine was uncommon in both establishing a lasting power base and in successfully exporting his rebellion to the mainland. Constantine moved quickly: he appointed generals in Gaul and crossed the Channel at Bononia (modern Boulogne). He took with him all of the 6,000 or so mobile troops left in Britain and their commander, the general Gerontius. The Roman Army of Gaul declared for him, followed by the civilian administration in Hispania (modern Spain and Portugal). The central Roman authorities did not respond to the Germanic invasion, while Constantine's forces got the better of at least one confrontation with the Vandals. Constantine also negotiated agreements with the Germanic groupings of the Franks, Alamanni and the Burgundians, thus securing the line of the Rhine. The main Vandal force and their allies moved into northern Gaul (modern Belgium). The Western Roman emperor, Honorius, and his commander-in-chief Stilicho, were in conflict with the Eastern Roman Empire and had a tenuous alliance with a large force of Visigoths under Alaric. Caught between different threats they sent a small army led by Sarus the Goth west to put down Constantine's revolt while Stilicho's main army waited on events. Sarus defeated one of Constantine's armies in a pitched battle. Constantine then personally moved against Sarus, but was besieged in Valence. Another army, led by Gerontius and Edobichus and largely made up of freshly recruited Franks and Alamanni, arrived to relieve Valence after a week of siege. Sarus was forced to retreat into Italy. With this success Constantine established control over most of Gaul and the Alpine passes into