Command and Conquer: Generals – Zero Hour (stylized as Command & Conquer: Generals - Zero:Hour) is the expansion pack for the computer game Command & Conquer: Generals. 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, General Leang.
Zero Hour also contains 3 new campaigns of five missions each, one for each side, with their chronological order being USA first, GLA second, and China last. 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 behind the current mission. The plot behind the Zero Hour campaigns picks up where it left off at the end of the previous campaigns.
At the beginning of the USA campaign, the Global Liberation Army (GLA) launches a biological weapon using a refitted Soyuz launch station from the captured Baikonur Cosmodrome in Kazakhstan at a USA military base located in Northern Europe. The United States military retaliates quickly, destroying the launch platform, before the GLA can fire another missile. As the campaign continues, the United States learns that a GLA general codenamed "Dr. Thrax" has been developing a more lethal variety of anthrax known as "Anthrax Gamma". When the USA locates his base of operations, they discover that he is planning on launching several missiles loaded with this toxin at major population centers within the USA itself. A swift strike by the USA, with the help of rogue GLA forces, succeeds in preventing this atrocity, and brings an end to "Dr. Thrax".
In the GLA campaign, the GLA, though disappointed by the death of Dr. Thrax, receives a boost in morale with the successful appointment of their new leader, General Mohmar "Deathstrike". The GLA first attempts to reunite its splintered factions under Deathstrike's command, which it succeeds in doing after eliminating the defector Prince Kassad's forces in Egypt, and then begins a fervent mission to drive the Americans from Europe. Despite their lack of technology, the GLA succeeds in inflicting tremendous harm against the USA, by capturing an American particle uplink cannon which they then use to destroy the USS Ronald Reagan (splitting her in half from starboard to port, as shown in the game's cover) and infiltrating the US West Coast to steal toxins from a chemical storage facility. This reaches its climax when the GLA overruns the USA’s European central command base in Stuttgart-Vaihingen, partially with the use of captured Chinese weaponry. The GLA's primary objective accomplished, they now begin to invade a vulnerable Europe and create a new repressive state.
In the Chinese campaign, the Chinese People's Liberation Army (PLA) sends its army into Europe to relieve the USA and gain revenge against the GLA for their humiliating use of Chinese technology in the capture of the German military base. In order to prevent the GLA from making use of advanced USA weapons, China launches a nuclear missile at the military base, destroying it, and then sends its forces into Germany, where the GLA invaders are concentrated. After a series of devastating losses, the nearly defeated GLA takes control of an evacuated USA military base and uses its weaponry against the Chinese army. China succeeds in destroying both the GLA and the captured USA base, and eliminating the GLA for good, rooting out their influence in Europe. Establishing the Eurasian Unity League with the newly liberated Europe, the world looks forward to a new era of Chinese leadership.
Each general has unique units and modifications to the standard arsenal.
- General Alexis Alexander: Alexander specializes in super weapons and fortification. She has Aurora Alpha bombers (which possess a fuel air bomb), a strengthened power grid (reactors can be upgraded to produce 300% more power, saving cost and build space), and EMP-enhanced Patriot base defenses, which instantly immobilize any vehicle and thus destroy aircraft instantly (however, like all missile-based weapons in Zero Hour, infantry is still almost invulnerable). Additionally, she builds Particle Cannons for only half the cost of normal. However, she cannot deploy main battle tanks, and all of her vehicles cost more. Alexander has great defensive capabilities, but has more difficulty in mounting a sustained offensive. She becomes stronger the longer that the game progresses, using multiple Particle Cannons to overwhelm her opponents unless the 'multiple super weapons' option is disabled.
- General Malcolm "Ace" Granger: His army specializes in aircraft deployment, and advanced airborne general abilities. He has upgraded F-22 Raptor called "King Raptors" (6 missiles vs standard 4), as well as cloaked Stealth Comanche attack helicopters (will decloak when firing), and all his aircraft are equipped with an automated laser missile defense system at no additional cost, which greatly improves their survival capabilities vs missile-based anti-air attacks (Shin Fai's MiniGunners and the laser-based USA Avengers are still the bane of aircraft, however). Malcolm also has access to Air Force affiliated Generals' Powers at lower ranks, such as the AC-130 Spectre Gunship. Finally, his aircraft are cheaper than normal. However, his forces cannot produce main battle tanks.
- General "Pinpoint" Townes: Townes plays more like the regular USA Army than the other two USA generals. He has modified Crusader Tanks called "Laser Tanks"; these are outfitted with a high powered laser cannon that exceeds ordinary tank cannons in firepower and fares better against infantry and structures, however, it has a shorter range. He can build the Laser Patriot Defense Turrets; Patriot Turrets outfitted with a Laser Cannon; this change makes the Laser Patriot effective against almost everything, including infantry as well as SCUD Launcher missiles. However, the effective base defense comes with two penalties: lasers require more power plants than a comparable number of standard Patriot Turrets, and if the base power drops below the minimum level, in addition to the standard base-operations penalty (defenses shut down, lower unit production speed, loss of radar, etc.), all of the General's Laser Tanks, regardless of their location on the battlefield, will instantly shut down as well until the power is restored. This makes the "Laser General" extremely vulnerable to attacks against the base power supply. He has no access to Tomahawk Launchers, making his attack force far less capable of long-range attacks or siege warfare.
- General Ta Hun Kwai: Kwai's general strategy is focused on the use of heavily armored, technologically superior tanks and vehicles. He is unable to build artillery units and must pay more to deploy aircraft and infantry. He has cheaper and more powerful tanks. Strategies involving reliance on heavy vehicle assaults and rapid troop movements are suited to General Kwai's forces. However, the overall lack of long-ranged support units leave Kwai's forces vulnerable to long range bombardment, against which his forces cannot effectively retaliate.
- General Tsing Shi Tao: Tao's army is boosted by nuclear energy. His nuclear technology enables more output per power plant than that of other Chinese divisions. He also utilizes a nuclear arsenal via missile silos, tactical nuclear artillery, and nuclear bomb equipped MiG fighter jets and Helix helicopters. His Overlord and Battlemaster Tanks fire shells that release nuclear radiation. In addition their movement speed is much greater than that of standard Chinese tanks due to nuclear engines which cause them to explode violently when destroyed. Other than these additions, there are no significant changes, and Tao's forces play much like the mainstream Chinese Army.
- General "Anvil" Shin Fai: "Anvil" specializes in Infantry units, and has a significant early tactical advantage against the infantry of other Generals. All infantry under his command start as veterans; He also can requisition elite minigunners to replace the standard Red Guardsmen. These high-caliber weapons they carry are the bane of aircraft in larger numbers. However, he is unable to build heavier battle tanks, but is still able to deploy primarily anti-personnel and support vehicles. This reliance on infantry leaves his force very vulnerable to the effects of radiation and toxins; and under less common circumstances, mass vehicle rushes, where infantry are vulnerable to being run over, yet, if his abilities and advantages are used properly and efficiently, will bring swift defeat to opposing forces. He is not faced in the General's Challenge, though a map and audio taunts for Fai's challenge were included.
- General "Tigress" Leang : The final general in the Generals' Challenge. She has a massive army consisting of units & structures of all factions, in addition to a Particle Cannon, Nuclear Missile, and Scud Storm. She is not a playable general. However, she can be unlocked as a playable general in different incarnations by several modifications. This is unconfirmed but her accent and audio taunts suggest this.
- "Dr. Thrax": The GLA Toxin General's units and some structures are boosted with toxins, and he sacrifices very little for his tactical advantages when fully upgraded. Most notable of advantages, is the fact that his units are granted the more potent toxin, Anthrax Beta (a late-game upgrade) from the beginning of a match, and can upgrade Anthrax Gamma (Anthrax Gamma is an effective weapon that can destroy tanks), to improve his forces further. He is able to train Toxin Rebels. The toxin-dispensing weapons of these units are equally effective against vehicles and infantry. His Tanks, RPG infantry and Stinger Sites also add a "stream" of toxin to their rockets, which adds a large damage bonus to their attacks.
- Prince Kassad: A GLA General specializing in stealth tactics. All of his buildings can be covered in camo netting, making them invisible to most enemy units, he gets an improved GPS Scrambler ability, allowing him to cloak more units than other GLA cells can in a period of time, and has improved stealth rebels. He also has cheaper Hijackers from the start, that are always stealth. He cannot build main battle tanks, or long range SCUD launchers. Ambush, surprise, harassment and attrition are the optimal strategies for Kassad's forces. However, the lack of heavy armor leaves them even more vulnerable than regular GLA cells to direct and concentrated assaults. Also, the inability to deploy long range SCUD launchers means that at most times, his forces operate without in-direct fire support. The stealthy presence of his forces provide a psychological edge over human opponents, but AI can somewhat detect the player's presence without using satellite scans or other stealth-detecting devices.
- General Rodall "Demo" Juhziz: A GLA general specializing in explosives. Most of his field units and buildings are granted a self-destruct capability, encouraging the use of suicide attacks. His Terrorists are more powerful and has cheaper, more powerful Demo Traps. His Combat Cycles comes with a Terrorist instead of a Rebel. He does not have access to most stealth units or Anthrax weapons. He also does not face the player in the Generals' Challenge.
- General Ironside the boss general of the USA forces.
- General Mohmar "Deathstrike" the boss general of the GLA forces, he is never fought, but appears in first mission of GLA campaign as an objective you have to defend.
- Colonel Burton, the hero character of the American army, he has the ability to kill enemy infantry units with a knife, and to plant timed and remote C4 charges. He is armed with a heavy machine-gun, though the guide book calls it a "sniper rifle". He is always stealth, except when he shoots and plants explosives, and can climb cliffs.
- Black Lotus, the hero of the Chinese army, has the ability to stop vehicles using her hacking abilities, to capture enemy and tech buildings, and to steal money from enemy supplies posts. She has no attack abilities though, which makes it imperative that she always be kept stealth.
- Jarmen Kell, the hero of the GLA, is a sniper, much like the Pathfinder of the American, but he remains stealth even when moving. His special ability is to snipe the driver out of an enemy vehicle, leaving it open to infantry units to enter. However, when you play as the GLA's Demolitions General, he has the ability to place timed and remote C4 explosives, much like Colonel Burton, and he can also suicide bomb, just like all other Demolitions General units after buying the "suicide" upgrade.
The large fan base around Zero Hour has developed both partial and complete modifications of the units, maps, missions, etc. These include Blitzkrieg II, Contra, ShockWave, Cold War Crisis, Destructive Forces, Project Raptor, Remix. Command and Conquer All Stars , Command and Conquer Rise of the Reds , Red Alert 3 (a mod that copies all of the characters in Red Alert 2: Yuri's Revenge) , and Vietnam Glory Obscured .
Many of these modifications add units into the game which may bear a resemblance to real world military units. The "Zero hour reborn" mod contains some famous generals from real life. Mid East Crisis mod contains the factions of Israel and Syria. Naval Wars modification enables Naval units to be created in Zero Hour (Amphibious Transports, Patrol Boats, and up to two Battleships).
One to note is a modification called "All Stars" that combines all the C&C universes together, along with all up-to-date factions of each series (excluding the Scrin and The Empire of the Rising Sun). This modification by fan development team Command and Conquer Labs  was ranked #12 on Gamingbolt's list of "15 Mods that Changed PC Gaming," the only C&C mod to receive such an honor.
In late 2009 a small but very effective AI script mod was revived by users on fan community site Generals World, the mod was left in 2005 by its author as an age old "Advanced AI Mod" from user "Lion" who recently retired from his own RADEN and CNCDEN community sites; The users updated the mod with fixed bugs, lag optimizations, new features, and much more, making the AI experience and gameplay much better. The new "Advanced AI Mod" received several updates, with the latest one on April 20, 2010.
Command & Conquer: Generals – Zero Hour includes online play through GameSpy on Windows, or GameRanger on Macs and Windows. The two services are not compatible. For the former players must first create a free GameSpy account in-game. Once in the main online lobby, players can choose from a number of options, including Quick Match, where players can have themselves matched up with other players of similar skill for 1 vs. 1 games, and Custom Game, where players can create their own games with the settings they want, and wait for other players to join them. The latter, though also free, is more of a manual process, and requires players to make, match, and start games without the benefit of an active central server to record stats, etc.
Custom games can have up to eight players playing in one online game. Performance may decline in games with large numbers of players, however, due to the computation, memory, and communication demands of larger games. It is to be noted, though, that the Zero Hour expansion has a noticeably more efficient engine than the original Generals, so games run more smoothly than compared to the original Generals. Lag and failed connections do, however, remain a problem online, as do mismatches when playing across ADSL and Cable internet. A common problem includes not being able to connect to anything ever at all times of the day. Some members of the community speculate that a fault in the coding of the game exists, causing it to consume more and more resources over time causing low frame rates and multi player lag.
In order to allow for better performance in large matches online and over LAN, players are recommended to reduce their graphical quality settings. This heavily reduces the amount of lag, and the chance of a mismatch. In fact, failure in computers meeting the computational requirements of the game is the primary reason for lag and mismatches, as tests have shown that during battles with two or more people, the game only uses 5 kB/s maximum of bandwidth.
- Command & Conquer: Generals - Zero Hour Official website
- Command & Conquer: Generals World fansite
- Command & Conquer: Generals - Zero Hour wiki guide at StrategyWiki