Ilbranteloth
Explorer
Everything the GM does is through moves. In fact, once play begins that's really his only tool since he doesn't get any dice.
Let me digress and discuss moves a little first. In general, player moves are usually really generic. I find it better to think of a player move as a defined resolution mechanic that the GM helps the player pick from based on what the PC is trying to accomplish. "My character cuts the bottom of a vine and swings across the chasm" becomes a Defy Danger move with specific attributes involved for the roll.
The GM's moves are different than a player's, of course. Both sets are often very generic, but the GM's are even more so. Rather than a move of "Defy Danger" like a player may choose, the DM gets moves like "Reveal an Unwelcome Truth" or "Use up Their Resources". The GM makes a move whenever a player rolls a failure OR when the players are waiting for something to happen (or if the situation is irresistible -- like a character says "Piece of cake. What could possibly go wrong?"). GM moves are designed to keep the action flowing and don't really represent much more than the typical narration and action/reaction of the environment most games have.
Digression over. Let's suppose a fight between the PCs and a guard breaks out. One of the PCs attempts to hit the guard with a weapon (this is the Hack and Slash player move), but the player rolls a total of 4 on 2d6 + Strength. Oops, a complete failure result. The GM gets to make a move. He might decide the guard strikes back (Deal Damage move), raises a horn to signal the rest of the band (Show signs of approaching threat), turn tail and run (Shows signs of approaching threat, Put someone on the Spot if they get a shot to interfere, or Change the Environment into a chase), or the guard may have a specific move defined in the stat block that is appropriate.
Now if the player had rolled 7 - 9 instead of <=6, the GM doesn't get a move. The guard takes damage and something happens to the PC because of the partial success. The typical side effect is the PC takes damage as the guard hits back, but it can be any GM move specifically targeting the PC that failed that makes sense within the situation.
So if the same group is having easy success at the gate and the GM gets an opportunity to play a move, perhaps the PCs hear the tumult of people scattering and see the prize they've come for being taken down one hallway (Offer an opportunity/Offer an opportunity with cost). as the camp scatters as best it can.
It comes back to the GM being in control of the developing fiction and moves. Moves are defined in two categories: Hard and Soft. A hard move has immediate irrevocable consequence like taking damage, losing gear, etc. A Soft move adjusts the situation the PCs find themselves within often ramping up the danger of potential consequence of further failure. The general expectation is the GM uses a Soft move to get the players moving and a Hard move most other times especially in reaction to failures and partial successes. But there are no strong rules around whether the GM should use a Hard or Soft move since Soft moves are often a reasonable environmental response.
The primary way I'll call "Lead the horse to water and force it to drink". One of the GMing principles for Dungeon World is "Play to find out what happens". You're not supposed to plan too thoroughly and let the fiction go where the play experience takes you. But let's say I'm a GM who really really wants a particular scene to occur. Let's say I just watched Slither or Alien and I want the party to bring an outsider into the group that is acting as a host to a terrible evil so I can have it explode open at an inopportune time.
I want the inclusion of the Trojan Horse to be the PCs idea so that they will be caught off guard by the event when it does happen. Since I'm in complete control as to how the fiction responds and the scene unfold I can lead the group to the base situation. I design the Trojan Horse to be something that looks pitiable and something one or more of the players or characters is likely to respond to -- a sick pregnant woman, a lost and starving hound, whatever is appropriate and when the PCs try to approach/aid the creature I make a show of asking for a Move to successfully tend/befriend the Torjan Horse expecting at least a partial success and simple inclusion in the group from that point forward. The player fails the move. Now the expectation is I as GM will make a Move to reflect that failure and keep momentum going. As a move in reaction, it should be a Hard move resulting in a change where the gambit the PC was pursuing can't pay off. But I want it to happen so I make a Soft move. Instead of the creature dying/running off in the night/attacking or whatever, I introduce a secondary threat and give the PCs a chance to save themselves AND the Trojan Horse. If they fail again, I can continue to use a Move that doesn't prevent the adoption of the Trojan Horse into the group until such time as the group finally succeeds or I give up as my interference grows too blatant. If I gave up, I can simply introduce a new Trojan Horse in the next couple of scenes until I get the result I want.
Part of what I struggled with (and perhaps it's just because it never became second nature) is the design of the game itself.
The move mechanic still feels very, very foreign to me. Why do I have to have a "move" to blow a horn? Why isn't it just blowing a horn?
Does running mean you have to choose between shows signs of an advancing threat, put someone on the spot, or change the environment, or can all three occur? Why can't they just turn and run, and the players each tell me how they react?
Overall, it just felt to "gamey" to me, like the focus was on following the rules, rather than just following the characters. One of the main reasons I've yet to find a video game, as immersive as they are, provide anything remotely like the experience of playing D&D since literally almost anything can happen.
I understand the concepts behind the system (at least some of them) and that the focus is on keeping the action flowing. Part of it is because I don't consider a primary purpose of being a DM as keeping the action flowing. Yes, I want to ensure that things don't get stuck, but really I see it as the PCs responsibility to keep things flowing. I'm not interested in making a soft move to move the characters along, because I think things are too slow, unless they are too slow because of a mistake I've made.
They are the ones making the decisions. So I let them do so without my interference.
Your example of the Trojan Horse is a good one in terms of showing that even games that are supposed to prevent DM overreach, it's going to be possible in just about any system you can design.