Tactical Insertion

A Tactical Insertion is an item of equipment that is available in Call of Duty: Modern Warfare 2. It is only seen in multiplayer. Tactical Insertions, sometimes abbreviated to TI, appear in the form of flares, which are placed where the player using the flare would like to be respawned. A crosshair-like chevron (^) is shown when the TI is being placed, and points in the direction the player respawning will face.

Tactics
It is generally more useful to use the Tactical Insertion in gametypes which requires defending an objective, providing respawns are enabled. It is useful to hide the TI in a corner or room away from enemies, who can destroy the flare, preventing the preferred respawn point. When a Tactical Insertion is destroyed, a message will appear in the corner showing who destroyed the flare, along with a sound similar to the one when being stuck with Semtex. Placing a TI near an integral flag in Domination is an effective, and widely-used way to make the best use of it. Placing a flare near an objective in Demolition or Sabotage (although there is a respawn delay in the latter) can be effective in preventing enemies from defusing/planting bombs. Although there is absolutely no respawn use in Search and Destroy, as there is a message when a TI has been destroyed, placing one near an objective, and visually defending the other, a player can be alerted when an enemy is at the other bombsite - this only applies if the enemy is inexperienced enough not to know of the alert. A C4 is often more useful than doing this, as it has lethal capabilities. In Capture the Flag, it can be useful to place one before taking the enemy flag, but can be hindered by the respawn delay. TI's can also be used to hold down preferred positions in the map which may be difficult to get to, such as the roof on Highrise. This can sometimes backfire if the TI is seen. One problem with placing a TI in a room or beside a wall is that it can glow through the wall, which makes it obvious to enemies, and makes it more likely that it will be destroyed. The best place to put the TI is somewhere hard to access by enemies, but easy for the user, and also closeby, such as the bathrooms in the house in Estate. A more unorthodox way of changing classes is to place a TI, commit suicide, and respawn instantly again with the new class, in the same position.

Repeatedly placing a TI in the same position can be detrimental to a player/team's performance in killing-based objective games, as players will realise the position of the TI, and either camp or place a Claymore in order to achieve more kills. Unless if they have Sitrep.

Some players prefer waiting until the enemy respawns where the Tactical Insertion was placed to get the kill.

A less common use is to drop a Tactical Insertion while defending a point in Headquarters. It will not help defending, but after the HQ is destroyed, a possible large cluster of enemies is likely to be nearby, and unsuspecting. It helps when battling for control of the HQ on large maps where the respawn points are dispersed.

Players have been known to wait by Tactical Insertion flares, hoping for a relatively easy spawn kill. 25 spawn kills from an enemy Tactical Insertion flare awards the "Tactical Deletion" (abbreviated TacDel) challenge and callsign title. Furthermore, SitRep makes Tactical Insertions show up red from any point in the map, even through walls. Tactical Insertion is unlocked at level 11. It is important to note that it takes about 3 seconds to light and drop the flare. During this time the user is defenceless against any attackers, but can cancel prepping the flare and switch back to their weapon. Tactical Insertion users can pick their flares back up to place them somewhere else if they so desire. Tactical Insertion flares can be destroyed by gunfire or manually by pressing X, F, or Square.

When respawning with a Tactical Insertion, one will be facing in the direction they were facing when they dropped the flare. Keep this in mind as not to drop on while facing a wall, only to respawn facing the same wall with your back to the enemy.

Killing an enemy within five seconds of tactically inserting five times completes the challenge Jack-In-The-Box I, unlocking the title by the same name. Jack-In-The-Box II requires 25 kills within five seconds of insertion and unlocks the Ta-Da! title.

Tactical Nuke boosters often use Tactical Insertions to get kills quickly and not have to go to the specific area where the players are Nuke Boosting. For example the Power Generators on Estate or the houses in the far corner of the map on Underpass.

Tactical Insertions are very useful to Snipers. You can spawn at or near to your chosen sniper position. This is a risk however, as if an enemy player sees the sniper using the TI or placing it on the ground they will most likely wait for that person to respawn and kill them.

Trivia

 * Friendly Tactical Insertions are green with the teams symbol, while enemy flares are red.
 * If the Tactical Insertion is stopped by switching weapons, the sound of the flare being prepped can be heard even when the other weapon is drawn, even though the flare is not dropped.
 * Tactical Insertions can be destroyed by gunshot, knife, killstreaks, falling airdrops, or if a player walks up to it and presses the action button.
 * Many glitchers use this, so they can spawn back into a glitch if they die, or at a point in a glitch which is hard to reach. They are also used by glitchers to achieve easy killstreak rewards such as the care package or emergency airdrop to utilize for glitching.
 * Tactical Insertions are also used by Nuke Boosting Players, easily allowing them to save time in finding the friend that they are boosting with. Counter Nuke boosters often use SitRep to track down their tactical insertions.
 * The Tactical Insertion can be concealed from enemies by deploying it in something with a red glow, like the heater in Derail.
 * The Tactical Insertion doesn't work in Search & Destroy, because you can't respawn after dying, although you can use it as a trap.
 * It's a good piece of equipment because it can be thrown in the HQ matches on the HQ so if you are killed you respawn in the HQ to keep capturing. But obviously the enemy doesn't have to detect it and destroy it, or, if you capture the base you can put a TI by it. Once you die and the other team takes the HQ, you can rush in and kill them all.
 * It is remarkably underused as it has to be redeployed after every use and it takes time to prep.
 * It is however useful to an extent in Search and Destroy, against inexperienced players mainly. If the player is defending the targets, they could place a TI at one target, and guard the other one. If an enemy player destroys the TI, then it will alert the player who placed it, so they will know where they are.
 * Tactical Insertion flares are very fragile and are easily destroyed by stray gunfire and grenades, so be sure to place them in an area where they aren't likely to be a victim of collateral damage.
 * A tactic that you can do is place it like a Claymore (in an obvious place) then when it says someone destroyed it run out and kill him or wait for him to come.
 * The flare that you fire at the end of the mission Whiskey Hotel is a complete reuse of the Tactical Insertion model and skin. It also has the name Tactical Insertion you can see it clearly if you do not have subtitles on.
 * Having the Martyrdom Deathstreak with a Tactical Insertion is not advised. The Grenade could destroy your flare, or even worse, kill you when respawning.
 * If you are killed by an enemy or kill an enemy within a few seconds of deploying a Tactical Insertion, your enemy will see you deploy it on killcam. It's best to wait a moment, or move the T.I. after a kill so your T.I. doesn't get smashed, or worse, you get spawn-killed.
 * A very good tactic, but not used by a lot of players is to use the Tactical Insertion as bait, just like a Care Package you don't desire to use. Put down your Tactical Insertion and camp by it picking off any hostile that is lurking around it waiting for you to spawn.
 * If you know an enemy is camping your T.I. after killing you, switching to a Riot Shield class gives you a better chance of surviving upon respawn.
 * Some players have been known to throw a Tactical Insertion over a friendly Claymore, so that a player will see the Tactical Insertion and as they run towards it to destroy it they will be unable to see the Claymore so will be killed by it.
 * Using a Tactical Insertion and One Man Army Pro, someone can shoot with their equipment (i.e. C4, Claymore, TI etc.). At the One Man Army Dialog, if someone presses the equipment button at the same time as the action button is pressed to change classes, the tactical insertion will be full laid down at the same time that you switch, so glitching the game into thinking that your primary weapons are equipment. In addition, each separate equipment has a different killfeed icon, such as an extended frag grenade or stun grenade (for C4 oddly enough). A link to a video explaining the glitch by MuzzaFuzza can be seen here.
 * Some players have dubbed themselves "Pity Players" and when they kill an enemy and find a tactical insertion nearby instead of waiting for him to respawn they will try to destroy it ASAP to give the unfortunate player a chance