Until I'd taken the trouble to examine the other diagram correctly, I took this one as being straightforward enough. Black has everything covered: he has the f-pawn adequately protected and White's central pawns are in no position to advance. Black's pawns, however, are in no position to move: and it is this sad circumstance that is his downfall, as it means that one or other of his pieces must move away from the f-pawn, or from f8 allowing the queen to move to that square and subsequently take on f7 (or worse). It is zugzwang: Black loses because of his compulsion to move.
Or is it? Is it really? I don't know that it is. Because I can tell you for certain that this is a won position for White whoever has the move.
I started looking at the position and wondering, what if it was White to play and he did play 1.d4? Black must play 1...Qxe4 which abandons the f-pawn anyway. So, 2.Qxf7+ Kd8 3.Qe6 and what's happening here?
Obviously Black can take the d4 pawn, but only at the price of allowing the d6-pawn to be taken, with a check that enables White to play a further check putting his queen somewhere like c6 that defends the remaining pawns. Or Black can play his queen onto f4 (and subsequently g3 or h2) and hope to defend the d6-pawn.
But in fact, he can't, because beginning with the paradoxical 4.Kh7, White can gradually manoeuvre the king closer to the Black pawn and eventually take it. The variations are far too plentiful for me to show them, as one might imagine where queen endings are concerned, but I am quite sure that eventually, we will reach something like this with White to play:
Now is that ending won for White? I don't know for certain. I do not possess the knowledge or experience of queen endings (or the tablebases) which would tell me. However, I am pretty sure that it is, it's certainly a good practical winning try and I'm sure if I reached that position in a game I think I would expect to win. Moreover, it's some distance away from the impression I previously had - that White, in the original game, could make progress only because it was Black's turn to play.
But there's more. There is a better line, one I confess I did not find myself and probably never would have done. (You might, in fact, like to try looking for it yourself before finding the answer below. I imagine it would make a very good endgame exercise - but only, I think, for the advanced pupil.) From the diagram, White to play, what is the best move?
What did you find?
My computer found 1.Qh6!!
Now there are rather fewer lines than before and they are rather more definitive:
(a) 1...Kd8 2.Qf8 exchanges queens and wins ;
(b) 1...f5 2.Qg6+! followed by 3.exf5 promotes ;
(c) 1...f6 2.Qg6+ Kd8 3.Qg7 Qe5 4.Kf7 wins the f-pawn. Now Black can win the a-pawn but White will win the d-pawn in advantageous circumstances, e.g. 4...Qe8+ 5.Kxf5 Qe5+ 6.Kg6 Qe8+ 7.Kf5 Qxa4 8.Ke6 and wins, or 6...Qg3+ 7.Kf7 Qxd3 8.Qf6+ Kc7 9.Qe7+ Kc8 10.Qxd6 and wins ;
(d) 1...Kd7 2.Qf8! Qg5+ 3.Kxf7 and the point, very hard to see in the original position, is that when White's king is checked he can put it on the eighth rank and then interpose with his queen.
I would love to provide you with an online play-through to demonstrate these variations: as it is, you'll have to use a board! But I think they demonstrate that in the initial position, even if it is White's turn to move, he still wins.
So - is it the compulsion to move, in the position above, which is the cause of Black's defeat? I really don't know. It is true that, having to move, he is obliged to dismantle his own defences. As opposed to the other diagram, where he had no defence in place, he does have one here - but, having the move, he cannot maintain it.
Now on one view, and it's a view I probably agree with, that is zugzwang. Let us have a look at Bennett's definition again:
In chess it is used to decribe a position in which a player is reduced to a state of utter helplessness. He is obliged to move, but every move only makes his position worse.On this definition, zugzwang merely requires that a player's compulsion to move compels him to lose. It is his move, and he must hand over his position to his opponent when he does: that is enough. Nor, incidentally, does it say that he must lose as a result of his self-inflicted disadvantage: he must just "make his position worse".
But there is a view that implicit in the concept of zugzwang is something else - that were it not the player's turn to move, he would not be forced to lose. Such as is the case in this simple position, for instance:
Black to play must move 1...Ke8 or 1...Kc8, both of which lead swiftly to defeat - whereas if it were White's turn he could make no progress, other than to inflict stalemate.
Clearly the first position is not of that type. Considered simply as a position, it makes no difference who is to move, White wins either way. But considered as a game position, the player to move must do himself harm.
To me, that's zugzwang: at the very least, it's an element of zugzwang, and I think it's more than that. But I can imagine a purist taking a different view.
Sometimes chess is all about facts. Checkmate is a fact, and a drastic one at that. But sometimes, in chess, it depends. Sometimes it depends what you mean. Is this zugzwang or is not? Does it depend what you mean by zugzwang - and if so, what do you mean by it? Is there any true zugzwang in Zugzwang?