The "Commentarii" cover the Gallic Wars over a period of 8 years, beginning with conflict over the migration of the Helvetii in 58 BC, which drew in neighboring tribes and the Germanic Suebi. By 57 BC, Caesar had resolved to conquer all of Gaul, and led campaigns in the east, where the Nervii nearly defeated him. In 56 BC, Caesar defeated the Veneti in a naval battle and took most of northwest Gaul. In 55 BC, Caesar sought to boost his public image, and undertook first of their kind expeditions across the Rhine river and the English Channel. Upon his return from Britain, Caesar was hailed as a hero, though he had achieved little beyond landing because his army had been too small. The next year, he went back with a proper army and conquered much of Britain. However, tribes rose up on the continent, and the Romans suffered a humiliating defeat. 53 BC saw a draconian campaign against the Gauls in an attempt to pacify them. This failed, and the Gauls staged a mass revolt under the leadership of Vercingetorix in 52 BC. Gallic forces won a notable victory at the Battle of Gergovia, but the Romans' indomitable siege works at the Battle of Alesia utterly defeated the Gallic coalition.