Historical Game:
Steinitz-Lasker, World Chess Championship, 1896-97
In this example, you get to see Zugzwang happen in the Middlegame.
Lasker (Black) has just moved his Rook, from e8 to g8, prompting Steinitz (White) to Resign immediately, owing to the following reasons ...
Reason 1 of 6
Here, it doesn't matter where White's Bishop goes to - any move away from its g5 square will result in catastrophe ...
Move 35, if White's Bishop were to capture (x) Black's Pawn, on h4; Black's Rook would sprint down to g2, putting White's King in "Check" (+) and triggering the following ...
Move 36, White's King evades Check, to h1; Black's Rook captures (x) White's Queen, on d2, revealing a Discovered Check (+), from Black's Queen.
Here, it doesn't matter whether White moves his King or Blocks with his Rook - he's still doomed, by the same, eventual result ...
Move 37, White's Rook Blocks the Check; only for Black's Queen to capture (x) White's Rook and put White's King back in "Check" (+).
Move 38, White's King can only escape, to g1; Black's Queen, then marches onto g2 and, backed by her c6 Bishop, issues the "Checkmate" (#).
So, that's ONE way that Black would Win (0-1).
Here's another ...
Reason 2 of 6
Move 35, if instead, White's f-file Pawn attempted to break for Promotion, starting with f6; Black's Rook would capture (x) White's Bishop, on g5.
That could result in ...
Move 36, White's f-file Pawn advancing to f7; but Black's Rook, once again, going down onto g2 and "Checking" (+) White's King.
Which would lead to ...
Move 37, White's Queen capturing (x) Black's Rook, on g2; only for Black's Queen to capture (x) White's Queen, on g2 and put White's King in "Checkmate" (#).
Another way for Black to Win (0-1).
Reason 3 of 6
Move 35, and should White's King step down, onto g1; Black's Queen would attack from h1 - a "Check" (+) protected by her c6 Bishop.
Move 36, White's King would be Forced to escape, to f2; allowing Black's Rook to capture (x) White's Bishop, on g5.
Black would have yet more of and advantage to crush White's resistance.
Next up is another way for Black to Win ...
Reason 4 of 6
Shouid White's Rook attempt to leave Rank 1, to any square above, While will quickly Lose ...
Move 35, say White's Rook steps up to f2; Black's Queen will rocket down onto h1 for another "Checkmate" (#).
Black would Win, again, (0-1).
But he would be done there, as Black has yet one more route to victory ...
Reason 5 of 6
Should White's Rook move anywhere along Rank 1, other than right, onto g1, White will get thoroughly slapped ...
Move 35, if White's Rook goes onto, say, e1; Black's Queen will capture (x) White's Pawn, on f5 - and snuff out that chance for Promotion.
Then, if on ...
Move 36. White's Bishop captures (x) Black's Pawn, on h4; Black's Rook would race down to that, by now, familiar g2 square, placing White's King in "Check" (+).
Move 37, to preserve his Queen, White's King would escape Check, down onto h1; only for Black's Queen to capture (x) White's Pawn, on h3 to "Checkmate" White's King (#) ...
And so, another Win for Black (0-1).
Onto the final reason, for White's early Resignation ...
Reason 6 of 6
Move 35, if instead, White's Rook steps right, onto g1; Black's Rook will capture (x) White's Bishop, on g5.
Move 36, White's Queen would then have to seize the chance to capture (x) Black's Rook, on g5; that would allow Black's Queen to step upwards, onto d6 and "Check" (+) White's King.
Move 37, if White's Rook then Blocks the Check, from g3; Black's h-file Pawn would capture (x) White's Rook, on g3 and put White's King in "Check" (+).
Move 38, with limited options, White's Queen would have to capture (x) Black's Pawn, on g3; but that would let Black's Bishop to cunningly slide up to e8 ...
That move, by Black, was to prepare for White's intended dash to Promote his h-file Pawn.
Move 39, White's h-file Pawn would start the race for Promotion, by advancing to h4; Black's Queen would take the opportunity to capture (x) White's Queen, on g3 and "Checking" (+) White's King.
Move 40, White's King would then be Forced to capture (x) White's Queen, on g3; Black's b-file Pawn would then advance to b5 ...
Indeed, it's a sacrificial move, by Black's Pawn, but one that'll contribute to an easy Win!
Move 41, White's a-file Pawn would have no option but to capture (x) Black's Pawn, on b5; a move that creates a clear path for Black's a-file Pawn to advance, down onto a4.
The sequence ends here, but you can easily count the square moves of both White's h-file Pawn and Black's a-file Pawn, to determine Black will get a Queen first ...
White won't be able to react in time and will be severely disadvantaged - at this World Chess Championship level, Black would be odds-on to Win this game.
Hence White's Resignation!