SG-1 encounters what they believe to be another SG team under attack on another planet, only to realize that they have stumbled upon a training exercise carried out by would-be soldiers of Apophis preparing to invade earth.
"Rules of Engagement" provides examples of the following tropes:
- All for Nothing: The training of the false SG teams turns out to be this.
- Blatant Lies:Teal'c: This is Colonel O'Neill. He is well-loved by Apophis.[Cue incredulous look from O'Neill.]
- Chekhov's Gun: The footage of Apophis dying in the SGC infirmary in "Serpent's Song" is used to convince first Kyle and later the rest of the recruits both that Apophis is dead and that he was never a god in the first place.
- Drill Sergeant Nasty: Kyle acts like this toward the rest of the recruits, including SG-1 at first. Given that he looks all of about twenty, O'Neill has a hard time taking him seriously.
- A Father to His Men: Kyle, who insists on going back, even in the midst of the Final Challenge when all his men will be armed with lethal weapons and out to kill, to try and stop them from dying for Apophis.
- First Blood: When Kyle is accidentally shot with a real staff weapon, Captain Nelson declares that first blood has been spilled as sign that the "final task" is upon them, and the recruits consequently embark on a battle to the death.
- HeelFace Turn: Pulled first by Kyle, once he's shown that Apophis was not a god, and by his men when they see the same.
- The Infiltration: The team learns that Apophis had planned to invade earth this way, by training human soldiers to use earth weapons and study the culture until they could "pass" as being from earth.
- Paintball Episode: Using intars instead of paintball guns, but the principle is the same.
- Spotting the Thread: The team realizes that the recruits aren't from a real SG unit because the patches on their uniforms simply read 'SG-X'.
- Stun Gun: The intars, which can be made to look identical to any real weapon but deliver a harmless energy charge that temporarily incapacitates the target.
- They Wasted a Perfectly Good Character: Kyle and his men had a great deal of potential, as some of the first human former followers of the Goa'uld to turn against them, as well as being US military trained. They are, of course, never seen ever again.