No object is gained in causing your pawn to reach your partner’s king-row, except that coming back it takes in reverse way.
It is therefore advisable when they meet to permit them to remain together for mutual protection, as in such position they command four squares-forward and backward.
Should pawns by repeated captures reach the adversary’s square, they become any pieces their player chooses to name, and such pieces cannot be taken except by a piece equivalent in rank, or by a king or queen ([Rule 8]).
As, however, it is next to impossible for a pawn to reach adversary’s square, seeing that it can only do so by repeatedly capturing antagonists, this advantage goes for very little.
A pawn on the return march should be marked by tying a piece of thread or a ring round its neck. But it will be found that but few, if any, pawns will have to be so treated, and this most likely will occur at the end of the game, when one or other of the kings is hard pressed, and the pawn is hastening to his assistance.
No player is allowed to expose either his own or his partner’s king to check, and, though he is not compelled to cover his partner’s check, it is advisable in most cases, when able to do so, as it will be found that when the king is checked by one adversary, the other will profit by it to obtain a piece and a position.
Bear in mind that in this game everything depends on mutual assistance and self-sacrifice. In nine cases out of ten the one who refuses to sacrifice in order to save his partner from checkmate brings speedy defeat on each.
Castling is not allowed; it is therefore advisable to get out one’s knights as soon as possible in order to give castles an opportunity of moving out of the way of a sudden combined attack.
Another advantage in getting out the knights is that their greatest value is at the beginning of the game.