Sentry gun is a Anti-Infantry Structure in Command and conquer Red alert 2 and Yuri revenge.It was a robotic gun turret that used a rudimentary AI to fire on enemy soldiers and leaves friendly ones unharmed. It was built as a Russian equivalent to the Allied pill box.

Despite the Soviet Union being known for its nigh-obsessive propensity for excess firepower, the removal of the unreasonably deadly flame tower from Second World War arsenal proved that the Russian military had some ability to limit itself. Realizing through the trials of the Second World War that the flame-thrower mounted watchtowers were as dangerous to Soviet troops as they were to Allied ones, the Red Army quickly sought out a suitable base defense to act as a safer replacement.

It was redesigned in the Third World War's third iteration, this time controlled by a conscript instead of AI.

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Utilizing AI technology, Soviet military scientists developed the sentry gun, an automated gun turret that fired 12.7 millimeter bullets at a blindingly rapid clip. Using a simple camera "eye" and early "friend/foe" programming, the turrets were able to detect who was a member of the Red Army and who was not via visual approximation, essentially telling the machine who to shoot and who to avoid shooting at. While designed mainly for killing infantry, something which they excelled at, the sentry guns were also fairly effective against lightly armoured vehicles and even did reasonable damage to their heavily armoured brethren. In suitable numbers, the turrets could combat most basic threats.