The two principles mentioned—namely the development of the pieces without unnecessary Pawn moves or other loss of time and the maintenance of a Pawn in the center—are a perfectly sufficient guidance in all King's Pawn openings, as no particular difficulty exists for any piece to be developed to a favorable square. Even if Black tries to avoid the well-known openings which result from the reply (1) …, P-e5 by playing (1) …, P- e6 for instance, or (1) …, P-c5;, or, in fact, any other of the twenty possible first moves, White will find the right way to mobilize his men if he strictly adheres to those two principles and resists the temptation to institute an early attack. A few examples will show how simple the application of the principle is.
I. (1) P-e4 P-d5
This attacks White's Pawn and White has to decide whether to protect, advance or exchange him. The advance P-e5 and the protection P-f3 are out of question because these moves are Pawn moves which do not contribute to the development and are, therefore, to be classed as mere loss of time. The protection (2) P-d3 is not sufficient either as Black, after exchanging on e4, would hamper White's development by exchanging Queens so that White would lose the right of castling. The protection (2) Kt-c3 cannot be recommended as Black could deprive White of his center- Pawn and obtain one for himself by Pxe4, (3) Ktxe4; P-e5. For all these reasons White cannot do better than exchanges on d5.
At first sight this might seem a violation of the principles, as Pxd5 is a Pawn move which does not further the development of the pieces while Black, in retaking the Pawn, develops his Queen. However, as was already pointed out on several other occasions, the early development of the Queen is not desirable as she is sure to be exposed to the attack of minor pieces. Indeed, White obtains the better game through (3) Kt-c3, Q-a5; (4) P-d4 or (4) Kt-f3, followed by P-d4. Black cannot get his King's Pawn up to the center [(4) P-d4, P-e5; (5) Q-h5] and in addition he is bound to lose some more moves with his Queen as soon as White has developed his Bishop to d2 threatening a discovered attack through a move with the Knight c3.
II. (1) P-e4 P-e6
With this move Black switches the center from the e-file to the d-file.
(2) P-d4 P-d5
Now White need not hesitate to protect his King's Pawn with Kt- c3, for Black cannot, as shown in example 1, gain control of the center by exchanging on e4 and playing P-e5.
The advance (3) P-e5 cannot be recommended for the reason explained in example I. Of course, White, being a move ahead anyhow, can afford to make a Pawn move which does not exactly advance his own development, if that Pawn move hampers the development of the opponent to some extent. This would be the case after (3) P-e5, as Black could not develop his King's Knight to the most natural square, namely, f6. However, the Pawns d4 and e5, though forming a strong center, as long as they are both in place, are liable to become subject to disagreeable attacks which Black can institute with P-c5 and P-f6, and if White cannot maintain his center, then the advance to e5 is mere waste of time.
(3) Kt-c3 Kt-f6