II. (1) P-d4 (2) Kt-f3
Kt-f6
The advance P-c4, which, as explained, is customary in Queen's Pawn openings, serves its original purpose only if Black has a Pawn on d5 so that White can open the c-file. Therefore, it is better for White to wait until Black shows what intentions he has with his Queen's Pawn. (2) ... (3) Kt-c3 P-d6
Black's last move clearly indicates that he intends playing P-e5 and not P-d5, and so White has no reason to expect that he will be able to open the c-file for his Rooks. Consequently there is no objection to his developing the Queen's Knight to c3, blocking the c-Pawn. (3) ... (4) B-f4 Ktb8-d7
This prevents P-e5 for the time being, and Black has to make rather complicated preparations, such as P-c6 and Q-c7 before he can advance the King's Pawn two squares. In other words, White completes his development more quickly than Black and he has consequently the better winning chances, provided, of course, he knows how to maintain his advantage in the middle game and in the end game.
THE MIDDLE GAME
It is not possible to draw a distinct dividing line between the two stages of the game which are called the OPENING and the MIDDLE GAME. Strictly speaking the opening comprises only such moves as are NECESSARY for the development of the pieces, and any move which a player--without being compelled--makes with a piece that is already developed, ought to be regarded as a Middle-game move. To give an example: If after (1) P-e4, P-e5; (2) Kt-f3, Ktc6; (3) Kt-c3, Kt-f6; (4) B-b5 Black plays Kt-d4, he deviates from the Opening and embarks on a Middle-game maneuver; for the Queen's Knight was already developed. This does not mean that it is bad under all circumstances to make a Middle-game move during the opening stage of a game. But only such moves should be considered in cases of this kind as a player is fairly sure to make at any rate within the further course of the game with a view to increasing the mobility of the piece in question.
This is the main point. A second move made with a piece must improve its position, otherwise, common sense tells us, it is surely bad. For instance: After (1) P-e4, P-e5; (2) Kt-f3, Kt-c6; (3) B-b5, Kt-f6; (4) o-o, B-e7 there is no objection to White's playing (5) R-e1 as the Rook will very likely want to get into action in the e-file in any case, as soon as the development has progressed with P-d4, Kt-c3, B-g5, etc. But if in an opening like (1) P-e4, P-e5; (2) Kt-f3, Kt-c6; (3) B-c4, Kt-f6 White plays (4) Kt-g5 for instance, or (4) B-d5, it is evident that he merely wastes time, for in the first case he places the Knight on a square from which he is sure to be driven away again as soon as the direct attack involved in his move has been warded off, and in the second case he moves the Bishop to a square which does not afford him any more mobility than the one on which he stood before. As a rule only Rooks or Knights are in a position, during the opening, to add to their mobility by a second move; the Rooks by occupying a file which is liable to be opened by an exchange of Pawns, and the Knights by occupying a square in the center of the board. The Knights are really more often under the necessity of making several moves in succession than any other piece, because they can never pass over more than one line at a time, and they may be required to hasten from one wing of the board to the other just as often as the other pieces. This is the reason why the most favorable spot for a Knight is a square in the center of the board; there he is always ready for an excursion to either wing.