Right. So that’s all you really need. A rule to cover concord. What happens when there’s a disagreement about what happens? You roll for it.
“I shot you.”
“No you didn’t.”
Resolve that disagreement by rolling.
Now apply that to any disagreements.
If the outcome isn’t obvious from the fiction, and the players cannot agree on what should happen next, roll. This is a really old idea, as far as RPG ideas are old. See the Perfected images from the OP. That RPG was devised in the late 70s.
But, as has been noted, this process can often feel rather unsatisfying in a few ways. This is a space where my "game-(design-)purposes" taxonomy is useful.
If your interest is solely in "Groundedness and Simulation," then FKR is potentially a godsend. The premise of FKR is that
at least 100% of the consistency, functionality, and utility of rules can be replaced with pure GM judgment calls and a simple impass-breaking method (e.g. "negotiate or roll the dice, higher wins.") If you believe this is true, then you can enter into an almost "pure" G&S experience, because the input is whatever makes sense within the described space (Groundedness) and the output is whatever can be reasonably extrapolated from that input, then fed back in as new input (Simulation), a dedicated exercise in naturalistic reasoning.
The problems come in if either you
don't accept the premise to some degree, or you want something other than G&S design. Unfortunately, most promotion of FKR has a tendency to be incredibly reductive about responses to the former, and blithely ignores (or, worse, insults) the latter.
For the former, the blithe, reductive dismissal essentially always takes the following form (in many different phrases, but the concept is nearly uniform):
Promoter: "FKR is just as good as rules, if not better! You get all the benefits rules give you, with none of the hassle or problems."
Critic: "I'm not convinced that you actually do get the level of consistency that actually having rules provides, and I think rules offer utility that
ad hoc adjudications can't."
P: "Oh, so you don't trust your GM? Well you should play with people you trust. Really, you shouldn't even be playing regular games with people you don't trust!"
This response
misses the point, and yet it comes up all the damn time. It is not a matter of "trust," in the sense of
reliance on the integrity of another. I certainly wouldn't game with someone that I believed was doing things I consider untrustworthy! It's why I speak out so strongly against GMing techniques I consider...well, exactly that, untrustworthy. But just because I consider someone trustworthy does not mean that I believe they will
always exercise sound judgment, remember and abide by past precedent, have sufficient knowledge of all potential topics, be unbiased and impartial in their decisions, communicate effectively (that's a big one), and fully and soberly consider
all of the possible consequences of their actions well in advance. Indeed, even for people I trust a great deal, I expect that most of these things won't be true a significant portion of the time, because humans are really bad at consistency, rigor, and impartiality...
unless they have something to guide them.
And guess what? That's exactly what rules are for. It also seems to me one of the things that gets overlooked in drawing the connection between actual "free
Kriegsspiel" and the "Free Kriegsspiel <insert R word of choice>" concept. The umpire in this new version did not simply dispense with rules entirely and have referees do whatever they wanted, whenever they wanted. Indeed, to be a referee, you needed to
already be an extremely well-educated officer with excellent battlefield intuition, communication skills, and an internalized understanding of exactly
why "original" Kriegsspiel had all the fiddly modifiers and rules and such. In other words, you DID NOT simply need the so-called invisible rulebook of "stuff I've thought about regarding combat." You needed significant exposure to the theory and practice of a difficult field
and the skills to demonstrate that knowledge and back up your decisions, so others could follow and agree with your reasoning.
Now, a few people describing this have admitted that "FKR" as a name is fundamentally a little misleading, in that it isn't really trying to
do what "free
Kriegsspiel" did for regular
Kriegsspiel just on the table top. Instead, the goal is (in theory) to draw inspiration from FK for the purpose of roleplaying. But even in that light, I find there's a painfully dismissive attitude toward rules
of any kind whatsoever, even though the only reason FK worked is because you had folks who had studied rules well enough that the visible rulebooks had become etched in their minds as invisible ones. Which just gets right back to a more general criticism I have of many claims in TTRPG stuff: what is familiar, what a person has used for decades and thus never needs to consult a book to know the process, gets all of its ills dismissed, excused, or even justified as somehow necessary, while anything unfamiliar or different gets held to task for even the smallest issues and mistakes and even genuinely good choices that are simply not obviously and directly beneficial.
As noted above, however, the other issue is that FKR is surprisingly narrow in what game-(design-)purposes it supports. As others said above, it's consciously, even aggressively un-"game-y." In my taxonomy, it rejects the very idea that you can have a semi-objective Score (measure of performance, in whatever sense is relevant), and thus rejects the possibility of pursuing the Achievements (tested performance: were you able to "Step On Up" as the Forge puts it, did you have thr mojo, etc.) Note that this is Achievement with a capital A, meaning something specific. Obviously, people can achieve their goals in
any game, that's not what Achievement means here. "We completed the Tomb of Horrors and
nobody died" is a statement about Achievement; "we eventually destroyed Acererak, though it was a pyrrhic victory, we all died in the doing" is clearly an achievement, but the flawed and tarnished "win" lessens the impact of the Achievement involved.
FKR can...sort of...work with Conceit and Emulation, but there are likely to be problems. Much as with the fourth of my non-comprehensive game-(design-)purposes, C&E is built around doing what you need to do in order to realize some
narrative end. Unlike V&I, however, C&E is about a narrative
theme or
premise to be explored: the titular Conceit. Superheroes is the go-to here, since it's a neat, clean package with a lot of obvious and known thematic commitments. But others work too; Trek-style technobabble in an overall positive and heroic universe, Star Wars science fantasy, Teen Wolf sexy monster drama, etc. And the problem is...a lot of the time, genre conventions don't play nice with the naturalistic reasoning that FKR prizes so highly. Everyone at the table will be feeling pressure to break the genre conventions because it would be easier, or more effective, or faster, etc. Having rules that enforce those conventions is actually pretty important for getting people in the mood, so to speak. Again, it isn't that this combo is totally antithetical, but they are often going to be at cross-purposes unless the whole group is
really on board for sticking with the core Conceit.
Finally, we have Values and Issues, which is related to "story now" if that term is useful to you. Unfortunately, FKR is about as opposed to this as it is to S&A. That is, Values are about defining what truly matters to a character (not just principles, but people, places, objects, organizatios, etc.), and Issues are those things being threatened with loss, damage, or even destruction. V&I tends to have several rules because it is often highly charged play, driving at core values of both characters and players and potentially getting very transgressive in the process. The (intended) freewheeling nature of FKR is not quite
completely incompatible, but strongly opposed to the kinds of structures that V&I usually relies upon in order to avoid having conflicts over what is happening, what is reasonable, etc. The irony, of course, is that
conceptually FKR is actually the most similar to V&I; but it is that very similarity which causes the issues, like two people who are
too similar, and as a result can't stand one another's presence.