What was the first "Team Fortress 2" update to include a war?

The first Team Fortress 2 update to include a war was the Sniper vs. Spy Update. This update introduced a rivalry between the Sniper and Spy classes, adding new weapons, maps, and game modes focused on these two characters. It brought exciting gameplay changes, including the ability for the Sniper to charge his shots for increased damage and the Spy's ability to disguise as a member of the enemy team. The Sniper vs. Spy Update marked a significant milestone in the ongoing evolution of Team Fortress 2, enhancing the diversity and complexity of the game by introducing a fierce conflict between two iconic classes.