What I like about this mechanic is that it breaks the frame of the game. By forcing the player to risk something very real—not just prospects for victory, because every wargamer wins and loses lots of games—but the time and experience already invested in setting up and playing the game and all the potential play that still remained.
Most Idiot Rules try to keep the wargamer in line by threatening the possibility of victory in some way—don’t cross this line or your opponent gains x amount of Victory Points, don’t abandon this city or you forfeit y number of reinforcement steps. The gamer has, at times, a choice and can balance the possible cost against the potential benefit.
Contemporary and Cold War wargames need to include the nuclear, chemical, and biological aspect, particularly in any hypothetical NATO/Pact conflicts. Leaving them out detracts from the sense of reality, but to allow their use without any penalty is equally unrealistic.
The solution, as Matt points out, is to put something more than victory or defeat at stake. When games model nuclear escalation via the “nuclear die,” players leave to chance the possibility that a strategic nuclear exchange can occur. Lob that tactical nuke if you must, or use that chemical or biological strike to bump up an attack to the next odds column, but if you do, there’s a possibility that it’s game over.
No winner, no loser, just finished. Pack the counters back in the Plano.
Given that it’s a fair investment of time and effort to set up a wargame and play through it, being forced to stop the game is a potent deterrent indeed. Only an idiot would risk it, which is a fair model of the use of nuclear weapons as well.