In 52 B.C. Julius Caesar, near the end of his war against Gaul, had one great enemy left – the charismatic Arvernian, Vercingetorix. Expelled from Gergovia, for being too rash, Vercingetorix raised an army on his own, and assumed the role of commander. His strategy against Caesar was simple -- use superior cavalry to harass the Romans and drive them away. Caesar, understanding his own weakness, compensated by recruiting Germans to strengthen his own cavalry units. After a series of reversals, Vercingetorix was forced to retreat to the walled city of Alesia with his army of 80,000.
No obstacle would deter Caesar, however. He knew direct attack was impossible because of the hilltop position of the city, so he planned a siege to starve the Gauls into surrender. Caesar had 12 legions with auxiliaries ready to bring to bear on the enemy. It was mid-summer, 52 B.C.