He didn’t move units. He didn’t attack. He simply renegotiated a peace treaty that had been signed 300 years before he existed.
If you have never played it, install it. Set the difficulty to Warlord. Turn off the fog of war. And watch your first Warrior get killed by a Barbarian horseman on turn 5. Welcome to the jungle. You’re going to be here for a while. Sid Meiers Civilization 3 Complete