A dangerous passed pawn in center
Please look at the following pawn structure.
It is a very popular pawn structure, which can come up from several openings. For example from the Semi-Tarrasch and Queen`s gambit accepted, but also from the Greenfield opening (with pawn on g6)
Normally it leads to a winning pawn endgame for black ( pawn chain f5, g6, h7 seems best)
Endgames in general would be in black`s favour cause of the outside passed pawn.
But before the endgame comes the middle game. And here the center passed pawn on the d-file can become to a strong weapon.
Here a famous example:
Spasski managed to win this position with tactics around the d-pawn.
So what to do against such a strong weapon as a center passed pawn?
A) The attempt to stop it as soon as possible
This would have been black`s favourite position. The passed pawn would have been stopped a la Nimzowitsch very effectively by the knight and the queen side advantage soon would become evident
B) The attempt to eliminate it