Command and Conquer: Generals - Zero Hour is the expansion pack for the computer game Command & Conquer: Generals. It was released one year after the main game and is currently in version 1.04.

Zero Hour added several new abilities to each side, and a new mode of play called Generals' Challenge. In Generals' Challenge the player takes on the identity of one of nine generals (three representing each faction) and does battle against most of the other generals, eventually confronting a powerful "boss" general. The expansion also introduces new characters (enemy Generals, and newscasters, who brief the player.)

Source: Wikipedia Article