The GLA uses the Baikonur Cosmodrome to fire a toxin warhead at a US naval base in Northern Europe, prompting the US to respond before another missile can be fired. The beginning of the US campaign relates to the GLA's success in the previous game. The plot behind the Zero Hour campaigns picks up where it left off at the end of the previous campaigns. Unlike the previous campaigns, which were noted by Command and Conquer fans for not having full motion video cinematic sequences during mission briefing, the Zero Hour campaigns return to that Command and Conquer tradition, each showing a live-action video of a news reporter of the respective side giving details about the situation and instructions for what to do behind the current mission.
Zero Hour contains 3 new campaigns of five missions each, one for each side, with their chronological order being USA first, Global Liberation Army (GLA) second, and China last.
Zero Hour added several new abilities and units to each side, and a new mode of play called Generals' Challenge, along with a lot more changes, new features and bug/glitch fixes. Command and Conquer: Generals – Zero Hour is the expansion pack for the 2003 video game Command & Conquer: Generals.
