After (1) P-e4, P-e5 the only Pawn which both players have to move to enable the development of all pieces is the Queen's Pawn, which obstructs the Queen's Bishop. Of course, it would also be possible to secure an outlet for the Queen's Bishop by advancing the Queen's Knight's Pawn one step; but in the long diagonal the Bishop is ordinarily not so well posted as the development of the Queen's Knight to his most natural square, that is c3 or c6 respectively, would block the way of the Bishop. The Queen's Knight is best placed in the c-file because on the edge of the board, in the a-file, he has less mobility; less squares are accessible to him. In order to place him in the d-file it would be necessary to move the d-Pawn, and as this would also give an opening to the Queen's Bishop the move of the Queen's Knight's Pawn is superfluous.
Before moving the Queen's Pawn the players will have to make sure that in advancing him they will not block the way of any piece. Consequently, White will not play P-d3 on his second move. He will first develop the King's Bishop. Of course, he will not place him on d3, obstructing the Queen's Pawn and thereby the Queen's Bishop. Neither will he play B-b5, as Black could drive him away from there immediately with P-c6, opening another diagonal for the Queen. The choice between the remaining squares, e2 and c4, is not difficult. On e2 the Bishop would be in the way of the Queen and his way would soon be blocked by the King's Knight, who for similar reasons to those given for the move of the Queen's Knight will go to f3 in preference to other squares. Therefore, the only move to be considered in case the King's Bishop is played at this early stage of the game, is B-c4.
White is not forced to develop this Bishop on the second move by any means. He could either play (2) Kt-f3 or (2) Kt-c3 or (2) P- d4. The objection to the latter move, however, is that after (2) …., Pxd4; (3) Qxd4 the white Queen is exposed to the attack of the Knight b8, which means loss of time. Kt-f3 or Kt-c3 are probably preferable to B-c4 on the second move, because it is certain that the Knights will not find any better squares on their initial move. The Bishop, however, may have an occasion to be used on b5 instead of on c4, and it is a good thing, generally speaking, to keep the option of moving a piece to different squares as long as it is compatible with the other requirements of the position.
That the Bishop may be used to advantage on b5 will be seen from the following variation. Supposing White plays (2) Kt-f3. Then the Pawn e5 is attacked. The only sensible protection is (2) …, Kt-c6; for P-f6 does not come into consideration, as it is a Pawn move which does not add anything to the development of the pieces; P-d6 blocks the Bishop f8; B-d6 obstructs the Queen's Pawn and Q-f6 or Q-e7 hinders the development of the Knight or the Bishop respectively. Now, it can readily be seen that after (2) …, Kt-c6 White may want to place his King's Bishop on b5, for with this move he repeats indirectly his attack on the King's Pawn through the threat to remove the protecting Knight. It is true, that this threat needs no attention as long as White's King's Pawn is not protected (for instance: (3) …, Kt-f6; (4) Bxc6, Pd7xc6; (5) Ktxe5, Q-d4 attacking Knight and Pawn at the same time and thereby regaining the Pawn) but as soon as White has defended the Pawn—with P-d3 may be—the Bishop b5 is at work and Black must seek additional protection for the Pawn e5.
If White, on his second move, plays B-c4, he attacks the Pawn f7. This Pawn is protected by Black's King and so he need not be defended any further; but Black must be on the alert against a concentration of some more white men on f7. White could try (3) Q-f3 or Q-h5. However, Black would then have time to defend himself with Kt-f6 or Q-e7 respectively.
Therefore, on the second move, Black may make any developing move; he could, of course, play (2) …, Kt-f6, preventing White's Queen from going to h5, but this is unnecessary, as Q-h5 would be a very bad move, placing the Queen on a square from which she is bound to be chased away very soon. For instance: (2) …., B-c5; (3) Q-h5, Q-e7 (not P-g6 on account of Qxe5 attacking the King and the Rook at the same time). Now, whatever White plays, he will have to retire again with his Queen as soon as Black attacks her with Kt-f6, and so he loses his birth-right of attack; for it will be Black who is a move ahead in the development instead of White, as it ought to be.
If both players refrain from premature attack the game might develop as follows: (2) B-c4, B-c5; (3) Kt-f3, Kt-c6; (4) P-d3, Kt-f6; (5) Kt-c3, P-d6; (6) o-o, o-o; (7) B-g5. This move is the first one with which White trespasses the "frontier" which may be said to run in the openings of all games between the fourth and fifth ranks of the board. The Bishops are the only pieces for whom there is a field of action in the opponent's camp early in the game. They pin a hostile Knight and thereby exert a certain pressure on the opponent who naturally does not like to see any of his pieces deprived of its mobility. The fact that Black can drive White's Bishop away with P-h6 does not lead to any loss of time for White, for the Bishop can retire to h4, still maintaining the pin, while Black has not furthered his development by his Pawn move; in fact, he has somewhat compromised his position and as explained by the discussion of the position of Diagram 37 the advance of the Pawn g7 to g5 cannot follow without the risk that White will uphold the pin even at the cost of a piece and obtain an overwhelming attack.
That the move P-h6 creates a weakness even if it is not followed up by P-g5 will be demonstrated later on in the discussion of the middle game. The correct answer to White's seventh move is easily found with the help of the principle of development. If White did not threaten anything Black would certainly think of nothing else than the development of his Queen's Bishop, the only minor piece which has not yet moved. Therefore, the first thing Black should consider in countering the threat involved in White's last move is a protection with a move of the Queen's Bishop. White's threat is (8) Kt-d5, attacking the Knight f6 for the second time. Although the Knight is twice protected, Black will naturally endeavor to prevent an accumulation of hostile pieces on the point f6, and he can do that indeed very easily by playing (7) …., B-e6 with a view toward capturing the Knight if he should move to d5.
The exchange (8) Kt-d5, Bxd5; (9) Bxd5 is manifestly not desirable for White, as it does not improve in any way the mobility of his men. On the contrary, White loses a move, as the result of the maneuver is only a change of location of the King's Bishop who was already developed while the principle of speedy development demands that no piece should be moved twice in the opening until ALL pieces are developed.
Unless Black's move involves a threat which needs immediate attention White should consider only such moves as will secure a possibility of development for his Rooks, that is maneuvers which are liable to produce an open file somewhere on the board.