Decima

by Mike Nelson

Introduction

Decima is an entry in the 10-Chess Contest. It features quite a few tens: 10x10 board, 10 non-pawn piece types, and a unique objective: getting pieces worth 10 or more points on the tenth rank.

Setup

Each player has one of each of the six compound pieces, two of each of the simple pieces, and six pawns.

Pieces

There are 10 piece types in this game (excluding Pawns) which consist of the four elemental pieces King, Knight, Bishop, and Rook and the six two-element combination pieces. Each piece has a point value, with the weaker pieces having the higher point values and the stronger pieces having the lower point values.

King (10 points)

Moves as in orthodox Chess, but is not royal, so it can be exposed to capture. Castling is not possible.

Knight (9 points)

Moves as in orthodox Chess.

Bishop (8 points)

Moves as in orthodox Chess.

Rook (7 points)

Moves as in orthodox Chess.

Duke (6 points)

Moves as the King or the Knight.

Pope (5 points)

Moves as the King or the Bishop.

Seneschal (4 points)

Moves as the King or the Rook.

Palladin (3 points)

Moves as the Knight or the Bishop.

Marshall (2 points)

Moves as the Knight of the Rook.

Queen (1 point)

Moves as the Bishop or the Rook.

Pawn (no points)

Moves as in orthodox Chess, including the double step on the first move and en passant capture. The Pawn has no point value, but on reaching the tenth rank promotes to any piece worth 6 points or less which the Pawn's owner has lost. In the unlikely event that the Pawn's owner still has all six of his 1-6 point pieces, the Pawn may not move to the tenth rank.

Rules

FIDE Chess rules apply except as indicated in these rules.

The object of Decima is to have one or more of your pieces whose point values total 10 or more your tenth rank at the beginning of your turn.

Moving a piece to your tenth rank which causes your point total to reach or exceed 10 is analogous to check--the opponent must capture one of your pieces and bring your total down to 9 or less on his turn. If the opponent cannot make such a capture, this is equivalent to checkmate and you win.

The capture of an opponent's piece on its tenth rank is a suicide capture--the capturing piece is also removed from the board. This applies whether or not the opponent has 10 points on the tenth rank.

Capturing your opponent's last piece wins, even if it is a suicide capture with your own last piece. A suicide capture with you own last piece is illegal in all other cases.

Stalemate, triple repetiton, and the 50-move rule apply exactly as in orthodox Chess. Stalemates are rare as they require the player to have no legal move wihtout any constraints on the movement of the King--in orthodox Chess most stalemates involve the prohibition on moving into check.

Playing Tips

The levelling effect is present in Decima in a peculiar way: the low point value pieces are the more powerful. They have more mobility and an easier time reaching the tenth rank; but they have little value for actually carrying out the win. Get the Queen, Marshall, and Palladin to the tenth rank and that's 6 points--you still need another piece. On the other hand, a King can seem to take forever to reach the tenth rank but can win all by itself. Most wins in practice involve two pieces.

Much strategy will revolve around finding the right moment to exchange or even sacrifice a high material value/low point value piece in order to allow weaker/higher point value pices to break through.

It is usually good strategy to give "check" often--as this requires the opponent to make a suicide capture, it will break down his defenses. Defense revolves around trying to keep any enemy piece from reaching the tenth rank.

On the other hand, sometimes the best defense is a good offense--if the opponent is overlooking his own defense while carrying out his all-out attack, you might find an opportunity for a quick counterattack. Sometimes sneaking a single piece down to the tenth rank is sufficient to turn the game around.

Much more strategy and tactics remain to be discovered.