Gallic existential concerns came to a head in 52 BCE and caused the widespread revolt the Romans had long feared. The campaigns of 53 BCE had been particularly harsh, and the Gauls feared for their prosperity. Previously, they had not been united, which had made them easy to conquer. But this changed in 53 BCE, when Caesar announced that Gaul was now being treated as a Roman province, subject to Roman laws and religion. This was a subject of immense concern for the Gauls, who feared the Romans would destroy the Gallic holy land, which the Carnutes watched over. Each year the druids met there to mediate between the tribes on the lands considered the center of Gaul. A threat to their sacred lands was an issue that finally united the Gauls. Over the winter the charismatic king of the Arverni tribe, Vercingetorix, assembled an unprecedented grand coalition of Gauls.