Requiring 25 consecutive kills (or 24 with the Hardline Perk), this killstreak is the hardest to acquire in Call of Duty: Modern Warfare 2. It can be unlocked as early as level 10.
Once used, a ten second countdown will display on all player's screens as the nuclear warhead, although invisible, falls to the ground, and a siren will sound. Once the countdown expires, the entire battlefield will be engulfed in white light as the nuke explodes. Time will appear to slow, all vehicles and killstreak rewards will explode, and finally, all spawned players including the user, die on the spot. Oddly, chickens on maps such as Rundown and Karachi, do not die. A Tactical Nuke detonation results in an automatic win for the user and their team, no matter what the current score is - however if a nuke is called in a Free-for-All, when an enemy has more kills than the Nuke user, the Nuke will not give the user a win. Once a Tactical Nuke is called in, the current score will freeze. This means that the scores will not increase even if players capture objectives, or kill enemies. For example, if the score in Domination was 199 to 180 and someone calls in a nuke, the score will remain the same.
Because of how difficult the nuke is to obtain, many players "boost" in Free-for-All or even Team Deathmatch in order to attain illegitimate Nukes.
After the Tactical Nuke explodes, it will kill all players who are alive within 5 seconds of its explosion. This can greatly extend the user's killstreak, as long as they are one of the final players killed - and it does add to the user's Leaderboards Killstreak. However, this can be avoided by calling a controllable killstreak with a laptop (Predator Missile, Chopper Gunner, etc.) exactly when the nuke goes off. A player can also survive a Tactical Nuke while in Final Stand or Last Stand.
The Nuke does not kill players in a random order. The bomb is dropped off map. If standing at the edge of the map, looking out at where the bomb is dropped the player will see an explosion and shock wave almost identical to when the Nuke goes off in the Call of Duty 4: Modern Warfare campaign mission "Shock and Awe". The players will be killed in order of distance (closest to furthest) of the explosion.
- Upon detonation, all killstreaks will be destroyed, giving the player who called the Nuke the amount of XP they would normally get for destroying a killstreak.
- If the player activates the Nuke in Demolition while his or her team is losing, the player will not get the "Ultimate Sacrifice" challenge. This also applies in Free-for-All.
- A scrapped game mode was hidden in the code of Call of Duty: Modern Warfare 2 named Global Thermonuclear War. The objective was to capture the nuke, and the first team to obtain 100 points would win, at which point the Tactical Nuke would be automatically activated.
- Being killed by a friendly nuke will affect a player's permanent K/D ratio.
- Interestingly, the acquisition sound for the Tactical Nuke was originally going to used as a sound for players leaving during online matches. The sound is referenced in the files as "mp_player_exit_warning".