There is a well-known trap in the Bogo-Indian Defense that raises an interesting question whenever I show it to someone. The trap is as follows and involves a question of how White should recapture after a trade of Bishops by Black:
The question after this trap is always, “Well, why would White ever want to play Qxd2 anyway, exposing the Queen to an attack by …Ne4? Isn’t it obviously better to recapture with Nbxd2, simultaneously developing the Queen Knight?” This is an excellent question. It is best answered by examining some long-term issues in the middlegame arising from this opening.
Comparing Knight developed at c3 and Knight at d2
Knight at c3
First, we look at what can happen if Black mistakenly allows White to recapture the Bishop with Qxd2 instead of Nbxd2, by not taking White’s Bishop early enough for the “trap”.
Black’s plan in this variation of the Bogo-Indian is to play …d6 and …e5, attacking White’s Pawn on d4 and encouraging White to close the center with d5. After the center is closed, all attention must be directed toward Pawn breaks by either side.
White is acknowledged by theory to have some advantage in this opening, having more space and a lead in development, and can think about attacking either on the Queen side (with plans such as a3, b4, c5) or on the King side (with plans such as e4, Ne1, Nd3, f4). But Black has a solid position, and can aim for counterplay with …a5 with …Na6 or …Nbd7 aiming for …Nc5, and/or …c6, to prevent White from gaining too much ground on the Queen side, and perhaps preparing slowly for …f5 to further attack White’s e4 Pawn chain base.
Knight at d2
By contrast, let’s see what happens when Black correctly forces White to recapture the Bishop with Nbxd2.
below is a sample continuation, in which at move 13, probably White’s best move is the paradoxical undeveloping move Nb1! The Knight at d2 is not doing much, being blocked by White’s own c4 and e4 Pawns. More important, it is not controlling the important a4 square (that Black can possibly aim to occupy with …a4), and it is not controlling the b5 square that could also be important (in a later attack against Black’s c7 and d6).
But this retreat wastes two moves (the original Nbxd2 and the Nb1) before getting to c3. However, in the Qxd2 situation, White wasted a move with the Queen, which is not so well-placed on d2: White’s Queen is actually better placed on d1, where it controls a4, than on d2. But White’s Rooks are not connected, so White will eventually want to develop the Queen anyway, perhaps to c2. So overall, White has lost one move, net, and, and this does make some difference in White advantage, even in a closed position, because the extra White move in the Nc3 variation makes it that much harder for Black to catch up in development and begin counterplay.
The summary of the situation is that paradoxically, since White wants the Knight on c3 anyway eventually, “saving” time by recapturing with development by playing Nbxd2 actually ends up wasting a move because the Knight will have to spend two more moves to get back to c3. Knights are funny pieces because any time a Knight has a choice to go to one of two different squares, if it chooses to go to one of them, it will always require two more moves to get to the alternate square. This is something to think about when planning Knight maneuvers: it is efficient, when possible, to plan to get to a desired square with the smallest number of moves possible (given the tactical constraints).
The other point to remember is that “wasting” moves to get a Knight to a good square may be justified. “Backwards” Knight moves are very important in chess, because a Knight on a good square can be so powerful that it is worth spending the time to get the Knight there. Look at how White thematically “undevelops” the Knight on f3, where it is doing nothing, to e1 and then to d3, to control the c5 square and b4 square (in case of a Pawn advance to b4 in the future) and also regain pressure on Black’s e5 Pawn and help support an f4 advance.
Study of typical middlegame positions in the Bogo-Indian can pay off with better understanding of the roles of both of White’s Knights and both of Black’s Knights (Black’s King Knight was not discussed here, but it has plans too).