Generally, rooks are considered to be much better than knights. Why is that? Is it a myth or are they really better? Are there situations where a knights may be better that a rook? I usually think that rooks enter the game a bit later and this reduces their value during the early stages of the game.
Rooks are more suitable for open games where there are open lines. Knight are better for more closed games. Knights have the benefit of jumping over other pieces and rooks have the ability to move quickly whereas knights move very slowly.
Also, remember that you can't checkmate with just a Knight and King, so Rooks are probably more powerful in the endgame especially when the board is wide open.
There is always a situation where one piece can be better than another.
Rooks are superior to knights because they control more squares, and have more mobility. Also since they control whole ranks and files, they are able to bound the enemy pieces while knights and bishops are much more limited in that regard.
I agree with Xaisoft, and just want to add that in an open game, a rook can be very effective to reduce the opponent's pawns and keep the opponent's king "in place". While it is true that knights can be mobile in a close game, they are also very predictable. That being said, personally I'd be happy to see an opponent lose both of his/her knights.
Here are some things to consider when thinking about the strength of a knight vs. a rook (and much of this goes for other pieces in relation to the knight as well).
- At the height of their power a knight can only ever attack 8 squares. On an open board, if placed in the a1 square, the worst placement for a rook, a rook can attack 14. Due to its movement pattern it can take up to six moves to get from a corner square to a specific square on the other side of the board.
- A knight has a special condition that if it retreats from one square, it cannot continue to attack or defend the squares it was attacking or defending before its retreat. For instance, if a rook is defending e6 from e3 and is forced to retreat to e1 it still performs the job of defending e6. The same cannot be said for a knight.
- Knights do not cooperate as well as other pieces. There are many exceptions to this, though. This relates directly to point number 2. Two rooks can be a powerful force on an open file but the case is far more common that two knights can become "redundant" and get in each others way as a knight supporting a knight reduces the number of potential retreat squares of a fellow knight much more than two rooks supporting each other in most practical cases.
A major exceptions is the board positions with limited numbers of open files where one side will sacrifice the exchange (rook for knight) in order to gain a positional advantage, keep a knight from being strongly placed, or destroy the kings pawn cover and remove a defender. A common example of this occurs in the Sicilian when Black exchanges a rook for knight in order to continue his attack on the queen side.
FEN=2r1k2r/1b1b1ppp/p2p1n2/qp2pP2/1N2P1P1/P1NB4/1PP1Q2P/2KR3R b k - 0 1
17. bxc3 d5
18. exd5 O-O
19. Qxe5 Qxa3+
20. Kb1 Bxb4
21. cxb4 Nxd5
22. Qb2 Nc3+
23. Kc1 Na2+
24. Kb1 Nc3+
In general knight endgame theory is very similar to king and pawn endings. Normally if an attacker has a knight and pawn against a lone king the attacking side can easily win. But there is a special case of
K where the knight is unable to assist the attacking king because it suffers from an inability to lose a tempo.
Here Black's king is badly placed and cannot win even with the additional material.
FEN=7n/8/8/8/8/8/p2K4/k7 w - - 0 1
(1. Kc2? Ng6 2. Kc1 Ne5 3. Kc2 Nd3 White is in zugzwang
4. Kxd3 Kb2 -+)
4. Kc2 Ne1+
Endgame Positions where a Knight Defends against a Rook
Most positions where it is
K+R are draws. The only exceptions being when the knight is separated from his king and when the defending king is at the edge of the board and subject to mating threats.
FEN=3KN3/7r/8/3k4/8/8/8/8 b - - 0 5
As you should see the reason why a rook is considered stronger is due to the way the knight moves which means that it can never attack or defend as many squares as easily as a rook can. A rook can have power in long range or close range battles and is effective on both sides of the board, knights are only strong when well positioned on or near the 6th rank (for white). Rooks can be less effective in close positions and require on open file to be effective. Knights can thus be stronger in scenarios where there is only a single open or half open file and the game can be decided quickly by dynamic factors. These situations, however, are far rarer to the ones where the rook is stronger.
Ditto to most of what is being said. However let me add my 10 cents worth.
Knights are the coolest piece on the chess board. They can jump around and are unpredictable not predictable. Which way will the L be?
Yes you are right they are less effective on an open chess board with few pieces or on the edges of the chess board but how many times did you get the beautiful knight fork with check and ended up loosing your rook for nothing?
While a knight and king can not force mate, a night and a rook or a knight and queen are a different story altogether. What about the choking mate on the corner of the chess board with knight and queen? And please watch out for that knight check with a revealed attack on your queen or some other dignitary or else you will lose it!! King and queen forks? How many times have you had those in your Chess playing career? How did they effect the outcome of the game? Thanks to that elegant yet sneaky character called a knight.
What about the defensive strength of the knight if used properly? I've had games against amateurs when my knight held their queen at bay and protected my king. What about those tight games where you cant move? The knights are worth their weight in gold then aren't they?
Place a rook on a center square (on an open board). It can move to 14 other squares.
Place a knight on the same center square. It can move to only 8 other squares.
The ratio of a rook's value to a knights is 5 to 3, roughly that 14 to 8 ratio.
A rook is considered to be worth a knight and two pawns. Each pawn has two potential captures, plus an extra move (total of three). Two pawns plus a knight = 3+3+8=14, the movement factor of a rook.
Whether rooks are "better" than knights depends on the current position pieces on the board. One could say that a centralized knight that cannot be dislodged by enemy pawns may be "better" than a rook that is on it's original square and has no mobility. It may however, decrease in relative value if pieces and pawns are exchanged and the enemy rook moves to an open file for example. So in a few words, it depends on other factors like time, mobility, and which side has the initiative.
I forget the source, but a Knight on the 6th rank supported by a pawn (i.e. on an outpost) is worth a rook and a pawn or two. Although my personal evaluation for such a piece is "magnificent beast". It makes good sense, in certain situations, to trade such a knight for a rook in a closed endgame position, where another piece can then capture the pawn that was supporting the knight.
To add a further point:
Doubled rooks are exceptionally powerful as well as flexible, one can reposition them while maintaining the cover for each other which you cannot do with two knights.
Also the single to eventual doubling up rooks on the seventh file is typically a game winning technique which forks the pawn structure while serving as a solid base to assault the enemy king.