It happened that one day the Puzzles and Games Ring was sitting around after dinner playing two of its current favourite games when it occurred to them to combine the two to create a game with the best features of both. Thus was born shogammon.

(It should be noted that the Puzzles and Games Ring of the Archimedeans is the unsung intellect behind the game gess, which shot to fame after Martin Gardner wrote about it in Scientific American. But that was before the time of any of those then present.)

Anyway, the game. Shogammon is a nondeterministic strategy game almost, but not quite, entirely unlike some precursors of chess. It combines the tactical manœuvring of shogi with the mind-numbing strategic optimization of backgammon. Or something. You will need:

Rules of Shogammon

  • At the start of the game the pieces are set up as in shogi.
  • Turns alternate between the two players. On your turn, roll two dice. Each die roll corresponds to one or more types of piece: You may make one move with one piece corresponding to each of your two die rolls:
    • You may make the two moves in either order.
    • You must make moves if you can (if you can't you lose that roll). However you may choose in which order to interpret the rolls to determine possibility, so for example if you roll 6 and 1 you might move a pawn onto your king (see below) then claim that you can't move your king.
    • If you roll doubles you may make your two moves with the same piece or with two different pieces. You do not get four moves as in backgammon.
  • Pieces move as in shogi except that you may move onto a square already occupied by one of your own pieces. When you do this you stack the newly-arrived piece on top of the other to create a “point”:
    • Points consist of exactly two pieces: you may not stack a third piece onto a point.
    • Points do not move en bloc: the lower piece is simply immobilised until the upper one moves off. Of course, if you roll the right two numbers, you may remove the top one and then move the lower one within the same turn, possibly even reassembling the point on a different square.
  • You may capture single opposing pieces by moving onto their square as you would expect. You may capture an opponent's point by (and only by) rolling two numbers which would enable two of your own pieces to move onto the square it occupies within one turn: you then capture both opposing pieces and your own pieces form a point on the capture square.
  • Just as you can capture opposing pieces but not jump over them, similarly you may not move rooks and bishops over your own pieces without stopping.
  • As in shogi, you may drop a captured piece onto the board instead of a move when you roll the number for that type of piece. The shogi restrictions (you may not have two pawns in the same file and you may not drop a pawn, knight or lance where it can't move) apply. (Since there's no notion of checkmate there is no problem with dropping a pawn in front of the enemy king.)
  • Pieces promote as in shogi. Promoted pieces correspond to the same die roll they had before promotion. This can make for strategic differences between different promoted pieces even though they move the same way.
  • You win the game by capturing your opponent's king, whether in a point or individually.
  • There is no obligation to get out of check. If you end your move with the king under attack, you can jolly well pray that your opponent doesn't roll the right number or numbers. If your opponent will win next turn whatever the dice roll ... I guess that's checkmate.

(Very) basic observations on Shogammon strategy

Putting the king in a point is rather like castling in chess: it adds security at the expense of mobility, especially if the king is underneath. In this case your opponent will pile up pieces besieging the point just waiting for a lucky roll, and it's difficult to do anything about this except win first.

A better alternative is to keep the king as the top piece of a point, so it has a decent chance of wandering around a bit to keep your opponent on its toes. Of course this temporarily incapacitates another piece, but hey, you have nine pawns you can use. You can even drop pieces by your king to give it a path of potential points leading in any desired direction.

Bear in mind that whenever you roll a 6 you're forced to move your king (unless it's under another piece), so you should try to keep at least one single piece next to it it can move to. Preferably not an important one: who knows how long it might be stuck there.

Real sadists may like to play series of games with a doubling cube.

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