“Rules of Engagement” is episode nine of season three of Stargate SG-1.
SG-1 arrive on a planet and find SG-11 there, and under attack. The team was not supposed to be there, and had actually been declared missing in action several months earlier. SG-11 is pinned down and when SG-1 try to help, they are attacked with some sort of unusual weapon in the shape of their MP5s that knocks the members of SG-1 unconscious.
They have been captured by children, who are wearing a badge that says SG-X, who are playing some sort of Goa’uld wargame – which Teal’c recognises. Apophis had been training troops in wargames to infiltrate and attack Earth using SGC uniforms.
SG-1 try to get the wargames to stop, especially as some of the children playing the games have accidentally picked up some of SG-1’s real weapons, not the stun guns. The children are strongly indoctrinated, and convincing them that Apophis is dead (really? He’ll probably be back, to coin a phrase).
Sort of interesting, showing how children can be brainwashed and how difficult it can be to break it.