In a recent tournament game that I painfully lost, I had a terrible losing position, but my opponent suddenly changed the nature of the game by allowing me to set up a blockade that should have enabled me to draw. I played carelessly and threw away the draw. I thought it would be instructive to show how powerful the concept of blockade is. In this game, the blockade was worth even more than the Pawn down and if I had been more careful, I could have maintained the blockade in the center and still had attacking chances of my own on the King side.
In the position below, my opponent had a winning advantage largely due to doubled Rooks on an open e-file, but then initiated a trade of Knights in which he blocked his own open file by recapturing with a Pawn to e4. Granted, this had its points: creation of a passed Pawn with Rooks behind it can be very powerful given the threat of advancing the Pawn further. But in this particular position, I had enough time to place my Bishop on e3 setting up a blockade, and if I had just made sure to leave it there, I could have continued a decent King side attack as compensation. Note in particular that Black’s extra Pawn, the d-Pawn is backward on a half-open file, and therefore if it can be prevented from advancing, the extra Pawn should not suffice to win in a simplified ending given enough piece activity. Here, tactics based on my good piece activity were enough that I could even have tried for more, if I had maneuvered my other Rook to the King side more efficiently.