A student showed me a fascinating game of his in which he was fighting for a draw as White, being an exchange down (Rook down for a Knight) for a Pawn. The position looked precarious, but the more I looked at it, the more it looked like he missed a fortress draw (he blundered quickly instead). Upon analysis, the fortress idea appears to work, but just barely. Below I explore the construction of the fortress and a subtlety that shows how a single inaccuracy could cause White a lot of trouble.
Features of the position
The starting position has unusual features that give White a fighting chance to draw at all:
- White has a Queen side Pawn majority and a King side Pawn majority. This helps prevent Pawn breaks by Black, although Black may be able to try a minority attack on the King side.
- Black’s b6 and e6 Pawns are extremely weak. If White could win one of them, that would ensure a lot of counterplay, probably good enough for a draw.
- White’s Knight on d4 is a monster. Most critically, it prevents any Black King invasion via c6, b5, or f5, so Black can any possibility of winning only by using the Rooks and King side Pawns.
- There is only one open file for any of the Rooks, the a-file. If White takes it, White should probably be able to draw by perpetual check and/or winning the b6 or e6 Pawn (especially the e6 Pawn, in which case White would have a passed e-Pawn ready to march to e6 and e7).
- One of Black’s Rooks happens to be very poorly placed. It will take time for this Rook to get to the a-file and join up with the other Rook to try to advantageously trade one Rook and then aim to knock off any weak White Pawns that cannot be protected by White’s King or Knight.
Ideas of White’s fortress
Making a list of the features of the positions gives many clues about how White could possibly draw this position, as well as how Black can try to win it. Of course, general considerations are not enough: very careful tactical calculation is required especially when White has the opportunity to go all out to abandon everything and try to get to Black’s seventh rank with a Rook: if the attempt at a perpetual check (or other draw by repetition) and/or Queen promotion fails, White will obviously lose. In this article I don’t focus on the variations in which Black allows such penetration, but on the fortress itself, under the assumption that Black does not allow the penetration.
The first thing to do is to imagine that Black does trade off White’s remaining Rook. Black can always force a Rook trade if desired, so we have to at least be able to hold the draw if White’s Rook can no longer defend the whole range of White’s position, from Queen side to King side.
- Black’s King cannot make progress as long as White’s Knight stays close to d4 and attacks the e6 Pawn.
- If Black sacrifices the Rook for White’s Knight, that should not achieve anything because Black’s King is not close enough to do anything useful in the King and Pawn ending.
- The c-Pawn must remain protected: this requires either the King on the b, c, or d files or the Knight on e2.
- The e-Pawn must remain protected: this requires either Ne2 blocking a Rook on e1, or f4 creating a Pawn chain.
- The f-Pawn must remain protected: if the g-Pawn has been forced to advance to g3, then f4 creates a Pawn chain; if the g-Pawn has been forced to advanced to g4, the f-Pawn is best protected at f3 by the Knight on d4.
- The g-Pawn must remain protected: it has to go to g3 or g4, because otherwise it is too far away from White’s King and Knight, which ideally remain no further than the e-file, in order to guard against possible loss of the c-Pawn or possible invastion by Black’s King.
- The h-Pawn must remain protected: at h3 it is in big trouble because we assume the g-Pawn has to be advanced; at h4 it might be OK, protected by a Pawn at g3; at h5 it might be OK, protected by a Pawn at g4.
How might Black breach the fortress?
The main thing to notice is that if Black can get a Pawn down to h3 safely, without trading any Rooks, White is surely lost, because Black can first tie up White’s pieces on the Queen side, then trade a Rook just in time to get the other Rook attacking White’s defenseless Pawn on h2. Therefore, Black has the plan of g5, h5, h4, h3.
Also, if Black can force a Pawn trade of the g-Pawn and open a file on the King side (say by White being able to play f4 only after Black has already played g5), White is surely lost, because of the power of a Rook crashing through White’s position through that file and winning one or more remaining weak White King side Pawns with the help of the other Rook.
So the main variation below, which succeeds in setting up a defensive fortress, has White hurrying up to distract Black’s Rook away from the King side to defend the a-file, then playing h4 to permanently prevent the h3 plan. Note that it involves saving time by not defending the attacked h2-Pawn at all.
An interesting side variation, which may lose, involves White playing g3 to protect the h2-Pawn currently under threat, but permanently weakening the h-Pawn. Black can try the g5, h5, h4, h3 plan. If White just waits passively, the game is lost. There is a fiendishly complicated variation in which White abandons the fortress idea and tries to get counterplay at the cost of sacrificing the f-Pawn after redeploying the Knight to d6. This is scary-looking and I don’t actually know if White can draw with computer-perfect play, but it is White’s best try after starting the mistaken g3 idea.