| For those of us who grew up watching the original Star Trek series, General Order 24 has a very different meaning than the sanitized variant promoted by Paramount, and the uber PC universe that Trek has become.
General Order 24 was actually given during the episode A Taste of Armageddon which was first broadcast on February 23, 1967. In this episode, the Enterprise carries an Ambassador, Robert Fox (played by Gene Lyons) to the planet Eminiar VII to open relations. Membership is possible. But Kirk, Mr. Spock and others are quite unaware that Eminiar is, in fact, at war. Has been for two hundred years. Normally, that sort of thing would be readily apparant on the ship's sensors. But this isn't a normal war, full of explosions, craters and screaming wounded. The leaders of Eminiar VII, and its enemy, Vendikar, have realized that wars are really messy things. So they've decided to clean up the process a bit. Instead of launching real weapons, they launch computer attacks, using parameters that simulate real weapons. In essence, the whole thing is a big war game. But people do die.
You see everyone is in the computer, and unlike playing Quake you get only one life. If the computer declares you a casualty, you have 24 hours to report to a disruption chamber and commit seppuku.
So the Enterprise approaches Vendikar with shields down. After all, nothing warlike is happening. They ignore Vendikar's leader when he tells them they're in danger, because they think its simply an isolationist ploy. Nothing diplomacy can't solve. After all barging in worked in Japan for Commodore Perry, didn't it?
The problem is, that the moment the Enterprise entered orbit, it became a target. And Vendikar shot at it too. The computers promptly declared our favorite starship a casualty. Now the ship's entire crew has been declared a casualty, and has to report to a suicide booth. And, of course, Captain Kirk, Mr. Spock and Doctor McCoy are all prisoners, hostages to be used to encourage mass suicide
Naturally, the disappearance of the landing party has Scotty quite worried, and he decides shields are in order. And just in time, too as Eminiar decides they'd better destroy the Enterprise. You see, if the crew doesn't die, then Vendikar will decide the treaty has been broken, and will launch real weapons. That means real war, which doesn't offer all the conveniences of home.
During his hostage period, Kirk is able to give one order. He yells to Scotty "General Order 24, two hours". General Order 24 doesn't mean "take any action" necessary to Mr. Scott. It means overkill. Sterilize Eminiar in two hours.
That puts Eminiar VII's leaders in an untenable box. On one hand, they have a live starship out there with orders to kill them, and they can't stop it. For once, the Enterprise significantly outguns the bad guys. On the other hand, if they don't kill the crew they will be in a real war.
Kirk's reasoning was this: They've smoothed over the rough edges of war enough, that they've gotten used to it. No reason to quit. After all, this war is centuries old. Kirk gambles that a real war will scare them badly enough to actually put a stop to it.
Does it work? Well, that would be telling . . . You'll have to watch for yourself | 
