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Caesar’s Double Siege: Starving Alesia The Battle of Alesia is perhaps the greatest military engineering feat in history. Facing a massive enemy force inside a city and an even larger relief army approaching from the rear, Julius Caesar did the unthinkable: he built two walls and fought two armies at the same time. This video covers: The Trap: Vercingetorix's retreat to Alesia. The Donut Fortification: Caesar's construction of the circumvallation and contravallation lines. Ancient Minefields: Th