A backstab is a context-sensitive attack that a Spy can perform with any of his melee weapons. When a Spy uses any one of his knives to hit an enemy from behind, a successful backstab is performed, resulting in an instant kill in almost all cases, with the exception of invincibility granting effects such as ÜberCharge or the Bonk! Atomic Punch.
Should a Spy perform a melee attack that connects with an enemy while he is behind said enemy, a backstab will occur. Backstabs deal damage equal to 200% of the target's current health and are also always critical hits, resulting in a total damage of six times the victim's current health; while the critical damage can be negated, this does not stop the stab from being lethal unless the target has significant additional protection.
A backstab will trigger as long as the Spy is anywhere within a 180° angle behind the enemy, utilizing the enemy's current aiming direction as straight forwards. To indicate that a Spy is within the required range and angle to perform a backstab, he will raise his knife and turn it downward, primed for a kill. The knife will remain in this position until the target is no longer in reach, or the Spy attempts a backstab by attacking. The knife turns downward even if positioned behind a cloaked or disguised enemy Spy. As the Spy's melee weapons do not have a delay between the swing being initiated and the damage being dealt, as long as the knife is pointed downward, the Spy simply needs to attack for an instant kill to occur.
Like normal melee attacks, backstabs can be performed while disguised, though the Spy proceeds to lose his disguise whether the attack connects or not. Backstabs are nothing more than pure damage, and so cannot injure or kill invulnerable players. Buildings and Halloween bosses cannot be backstabbed.
Robots in Mann vs. Machine can be backstabbed just as normal players. In addition to this, if a robot is sapped, it can be backstabbed from any direction, not just from behind. However, giant robots operate much differently. Backstabbing a giant has a base damage of 750, but this is reduced to 25% of that (188) by default; each armor penetration upgrade restores 25% of the base damage, up to 125% of the base (938). Spies must therefore upgrade their knife in order to have a chance at taking out giant robots.
Various weapons affect backstabs in some fashion:
- Backstabbing with Your Eternal Reward or the Wanga Prick causes silent death. The victim will not scream, their body will vanish, and no killfeed notification is given to the victim's teammates. The attacking Spy will disguise as the fallen enemy almost instantly.
- Backstabbing with the Conniver's Kunai will take the victim's remaining health and give it to the Spy, up to a maximum of 210. This is offset by a lowered base health.
- Backstabbing with the Big Earner will fill the Spy's Cloak meter by 30%, regardless of which cloaking device is equipped. A backstab with this weapon will also give the Spy a 3 second speed boost.
- Backstabbing with the Spy-cicle will turn enemy ragdolls into an ice statue, which also creates a loud freezing/cracking noise.
- Attempting to backstab a Sniper wearing the Razorback will result in the backstab being blocked, in addition to preventing the Spy from attacking, cloaking, or switching weapons for 2 seconds afterward. Thus, the Razorback makes Snipers less prone to backstabs and encourages Spies to use their selected revolver instead.
Fundamental Backstabbing/ Sapping Techniques
- Stab-and-Sap: Stab a (turtling) Engineer, before switching to your Sapper and sapping the Engineer’s Sentry Gun; this must be done fast enough that the Sentry Gun doesn't have time to turn around and kill you. An experienced Spy may track the Sentry Gun's turning direction and move against it after he stabs (as it will follow him, this will buy him more time), this set of movement is also known as circle-strafing. Using Your Eternal Reward can make the approach easier, as you instantly disguise upon a successful backstab, preventing the Sentry Gun from detecting you and retaliating; a Spy without a prior disguise must rely on cover to avoid the Sentry Gun's attention, as the Sentry will not be fooled by your instant disguise once it has already begun firing. This tactic is slightly easier on Engineers using the Wrangler, because the Sentry Gun is disabled for three seconds after the Engineer's death.
- Sap-and-Stab: Sap an Engineer's unattended building as bait, hide, then stab him when he returns to remove the Sapper.
- The Topstab: Sometimes paranoid Engineers will place their Sentry Gun and Dispenser in a fashion that allows the Engineer to have his back to a corner, making him seemingly protected from backstabs. It is possible to jump on this Engineer's head via climbing from his Dispenser or Sentry Gun while positioning yourself over the Engineer (facing the same direction as him) around his back until you get the "Knife-raised" animation, allowing you to score a backstab with a click.
- Quickstab: While an enemy is running towards you, let them run past you before spinning and stabbing their retreating back. This is one of the only reliable methods of backstabbing Scouts or any enemy that buys your disguise.
- Sidestab: As the name suggests, a side stab is accomplished by stabbing the back of an enemy from the side.
- Due to an in-game glitch, a stab that has appeared to have occurred from the front can sometimes be rendered as a backstab. Known more commonly as a facestab, these kills are now mostly the result of lag compensation by the game engine itself. Prior to many game patches, facestabs were more common due to bugs in the way the game detects a backstab. Facestabs take two forms: the "valid" stab and the "true" facestab. Most of what the recipient sees as a facestab is usually either a cornerstab or a sidestab, where on the Spy's screen, he sees it as attacking the target's back, but due to lag, the target sees the Spy attacking from the front. A valid facestab works as intended by the developers, making correct use of lag compensation. In a true facestab, the Spy appears to be attacking an enemy from the front on both players' screens, but lag compensation results in it being registered as a backstab. This is considered a bug. You can also perform a facestab when you are running directly at an enemy, while the enemy is running back on himself, this is because the hit-box of a player lags behind a little bit while moving back.
- Another community-coined term is the failstab, which refers to a backstab which should have succeeded but instead did only normal Knife damage, despite the backstab animation playing fully and the Knife connecting. These stabs are almost always linked to the latency conditions between the server and the player.
- Rarely, during taunts, the player's 'back' changes position; it becomes directly behind the player's 3rd-person camera, which means that players can avoid backstabs by moving the camera away from the Spy. This generally occurs by accident; for example, when you position the camera in front of you to watch the taunt yourself, making your back into your front. Facestabs can also rarely occur this way.
- The angle required for a backstab is based on the direction the victim is looking; however, all players have models whose normal stance has their backs rotated to the left slightly, due to the way they carry their respective weapons (this is most prominent with Heavies). This means that at certain angles you appear to be stabbing your target in the back, when in fact you are not inside the 180 degree angle for backstabs. Equally, there are valid backstab positions which appear to have you stabbing slightly into the front of your victim. These hit-box positions can be determined by the shoulders of the character models.
- When a player for the opposing team is standing on top of the Spy, the Spy can always perform a successful backstab regardless as to whether or not the Spy's aim falls within the regular backstab radius.
- Occasionally, when swiping at an enemy, the Spy will do the backstab animation, even if it wasn't a backstab.
- Originally, the Spy's backstab animation was just over a second long and manifested as the current animation, but was slowed down. This was changed to the current, sped up version used today in the interests of balance. Before this change, skilled Spies would "quick-stab". This involved staying out of backstab range of the victim, and then swinging the Knife just before entering backstab range, thereby bypassing the backstab animation but still rewarding an instant kill.
- Killing a player with a backstab will sometimes cause a special backstab death animation. This animation has a 25% chance of occurring, and varies from class to class. The Sniper performs this animation and sound during Meet the Spy.
- The Sniper's backstab animation was first seen in Trailer 2 before any backstab animations were integrated into the game.
- Despite dealing no damage, backstabbing an enemy who cannot be killed (Scout under the effects of Bonk! Atomic Punch or Übercharged enemies) deals a great amount of knockback that can easily be used to push the enemy into environmental hazards, such as off the side of DeGroot Keep, causing them to die while being invincible.