The Ruy Lopez Exchange-Keres Variation

 

After the 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6 dxc6, white has exchanged his light-squared bishop for a knight, which is a slight disadvantage in semi-open and open positions suh as this one, but on the other hand black has double c-pawns, which is usually a disadvantage. The latter depends on other factors. What factors might those be? For example, one can observe that given the following sequence of moves say 5.d4 exd4 6. Qxd4 7. Nxd4 we see that now black has no central pawns. Assume now that all remaining pieces are traded, and only pawns and kings are on the board. An illustration of that is given by the following diagram.

If that is the case then white has a signficant advantage since his pawn structure is much stronger than black's. After the moves f4 e5 f5 e6 he has good chances to create a passed pawn. This is the long term plan for white. Conversely, black's plan is to ensure that white will not be given the opportunity to reach a king and pawn ending with such a structure.

 

 

 

 

 

 

The key variations after 4....dxc6 are:

5.0-0

5.d4 Alekhine's variation

5.Nc3 Keres' variation.

Keres Variation 5.Nc3 is the least common, and that is why I will look at that first. Firstly, it defends the e-pawn, which as a result allows the move Nxe5 as Qd4 would have any signifcant threat. However, its main drawback is that it blocks the c-pawn for the moment, which would support a potential d4 advance. Now black has to attend to the threat of Nxe5. There are many ways to defend the pawn, directly or indirectly. The possibilities are

Direct:Qe7,Qf6,Qd6,f6,Bd6 

Indirect:Bc5,Bb4,Bg4

To save time and energy we can safely discard two of the above options as inadequate. These are Qe7 and Qf6 as Qd6 accomplishes the same goal while placing the queen on a square that does not obstruct king-side development.In fact it is the best move for black in my opinion, leading to an easy draw, and maybe a win if white plays carelessly. After 5....Qd6 white's best move is 6.d4. Why? If white hesitates and instead plays a normal move like 6. 0-0 getting his king to safety first, or 6.d3 black has the strong move 6...c5! stopping white's plans to open the center, trade off pieces as the endgame favours him, as explained above. Even if white tries to play c3 followed by the push d4 black has a way to stop this plan. To play c3, the knight has to move. If 7.Na4 black responds with 7...b5! expanding on the queenside and at same time driving the knight back to c3. If 7.Ne2 black responds with 7...Nf6 attacking the d-pawn. White plays 8.d3, only other move is the knight back to c3. After 8.d3 black responds with 8...h6 denying the g5 square for the bishop. In fact, the final position  gives black a big spatial advantage. The d-pawn cannot move as Nxe4 ends white's hope for a favourable endgame.

So we see that white must not waste time so he plays 6.d4. The last has brought one more attacker to the e5 square. Black must either defend it, otherwise he is going to lose the pawn and the game, or take the d-pawn. That is white's plan. To open the way for the e-pawn and hence create a favourable endgame position. If black tries to defend it with 6...f6 can either exchange pawns straight away, which would lead to the following sequence of moves: 6. d4 f6 7. dxe5 fxe5. Notice that effectively white has traded his d-pawn for black's f-pawn, bringing his long-term plan even closer to becoming real, as black's e-pawn is very weak, and white's king side pawn structure would be sufficient to force a win. So black plays 6....exd4. Now, white must either capture with the knight or the queen. Let's examine both options. If 7.Nxd4 after 7...c5 the knight has to move say 8.Ne2 as Nf3 would obstruct the f-pawn. Then 8...Qxd1+ and white has to recapture with the knight as Kxd1 would keep the rooks locked inside. After 9.Nxd1 black has gained some time which could prove crucial. So white decides to play 7.Qxd4. White has no problem trading queens for the reasons mentioned above (endgame). Black could play 7...Qxd4 8.Nxd4 c5 9.Ne2 but there is no need to rush. The best waiting move is 7....Bg4 exerting pressure on the defender of the queen. What black is trying to do is improve his position as much as he can at every move. After 7....Bg4 if 8.Qxd6 black responds with cxd6 improving his pawn structure. If 8.e5 after 8...c5 white has to play 9.Qd5 to keep the initiative and then after 9...Bxf3 white has to recapture with the g-pawn as 10.Qxf3 would leave the e-pawn undefended. So white's best move is 8.Be3 defending the queen. Black can then play 8...Bxf3 9.gxf3 and either continue development or trade queens.

To sum up, Qd6 has proven a solid move for black giving him good chances for counterplay while not allowing white to trade down significantly. If played correclty a draw is quite easily obtained. The rest of the game is more tactical than positional.

 

 

 

 

 

 

 

 

 

 

After 5.Nc3 f6 6.d4 (already discussed what happens if white hesitates, the only difference that black cannot play Nf6. The key move after Ne2, to open way for the c-pawn as Na4 is followed by b5 driving it back to c3, is Bg4, play out the variation and see for yourself.) Actually the position will be very similar after 5.Nc3 f6 6.d4 exd4 7.Qxd4 (if 7.Nxd4 we have already covered this case after 7...c5 the knight has to move 8.Ne2 Qxd1+ 9.Nxd1 falling behind.) 7....Qxd4 8.Nxd4 c5. So the position is the same only that now black has played the move f6 as well giving him a better position. This move may block the knight at g8 but it prevents e5, for the time being. So, one could support the idea that f6 is stronger than Qd6 as black has gained a move (not lose one by moving the queen twice). 

The move 5...Bd6 defends the pawn, develops a piece and blocks the d-file effectively denying to trade queens for the time being. You should know white's next move by now, 6.d4. Black has two options he can either simply recapture 6....exd4 which is the better move, or play 6...Bg4 pinning the knight. If white responds with 7.dxe5 black must first capture the knight 7....Bxf3 8. Qxf3 Bxe5. The material is even but black has traded his unopposed light-squared bishop for the less valuable knight. (generally knights and bishops have the same value, but bishops are usually more effective in open games, whereas knights are better at closed games). If instead black plays 6...exd4 then white has two choices, he can restore the material balance with either 7.Nxd4 or Qxd4. If 7.Qxd4 black has to respond to the immediate threat Qxg7. 7...f6 stops white's plans and then white will lose time since his plan is to push his king side pawns up the board. So 7.Nxd4 is the better option, and after blacks move say 7...c5 8.Ne2 does not block the f-pawn and also supports it at the f4 square. So all the options mentioned above lead to more or less similar positions. Check the three following diagrams:

Here is game played by two strong international grandmasters where white decided to employ the Keres Variation 5.Nc3. We see that black managed to draw the game quite easily. We could also argue that as it was the 1st round white decided to play cautiously as this variation has been heavily analysed and if played by grandmasters the most probable result is a draw. However, in lower levels, due to the fact the position is more tactical than positional, it is always possible for one side to slip and make a wrong move which could prove crucial for the game.