Sankaku Shogi

Sankaku Shogi

Sankaku Shogi (三角将棋, “Triangle Shogi”) is a modern Shogi-inspired variant designed by L. Lynn Smith in 2004. It is played on a field of 44 triangular cells. Each player controls 13 pieces. Unlike standard Shogi, captured pieces are permanently removed from play — there are no drops.

Board

The playing field is 44 triangular cells on files a–g and ranks 1–8. It began as a diamond: “the two far cells were removed to limit ‘choke’ points and create a form of first rank for each player”, and “the two cells on each side were removed to prevent direct lines of attack on the initial position of the Emperors”. From rank 8 down to rank 1 the ranks hold 3, 5, 7, 7, 7, 7, 5 and 3 cells. Along a rank the triangles alternate apex up and apex down, so neighbouring files share a slanted side.

Orthogonal movement is “through the above patterns of triangles”, the three strips the source draws: one along a rank and one along each slant, “with each step being from one cell to another which shares a complete side”. A cell has at most three orthogonal neighbours and six orthogonal directions, two along each strip. The second orthogonal is two steps along one strip.

Adjacent movement is “the translation from one cell to another which connected either by side or point”: every cell touching it at a side or a corner, up to twelve. The source illustrates it with the six triangles round one corner, any of which “could adjacently move to any of the other five cells”.

Starting Position

Black:

• Emperor: d1
• Chariots: c1, e1
• Cavalry: b2, c2, e2, f2
• General: d2
• Soldiers: b3, c3, d3, e3, f3

White:

• Emperor: d8
• Chariots: c8, e8
• Cavalry: b7, c7, e7, f7
• General: d7
• Soldiers: b6, c6, d6, e6, f6

Pieces

Emperor: Leaps to any cell on the entire board. Cannot capture an opponent Emperor that is defended (any opponent piece could recapture on that square).

Chariot: Slides orthogonally any number of cells. Cannot be captured by Soldiers. Can “run down” a Soldier: captures the Soldier and continues sliding to end on a vacant cell or capture another piece.

General: Steps to any adjacent cell (connected by side or point — up to 12 cells).

Cavalry: Leaps to the second orthogonal cell. If that cell is occupied by a friendly piece, the Cavalry makes one additional leap in any direction (not returning to start). The second leap must land on a vacant or enemy-occupied cell.

Soldier: Steps one orthogonal. May capture on the second orthogonal cell if the first orthogonal cell is vacant. Cannot capture Chariots. Mandatorily promotes to General upon making any capture.

Promotion

Soldiers and Cavalry promote to General immediately and mandatorily upon making any capture. There is no optional promotion and no promotion zone. Generals, Emperors, and Chariots do not promote.

Rules

• Black moves first.
• Each player must move every turn — passing is not allowed.
• All captured pieces are permanently removed (no drops, no recycling).
• Win: Capture the opponent’s Emperor.
• Repetition: A player may not repeat a position solely to avoid capture.

Attribution

Designed by L. Lynn Smith, 2004. Rules documented from chessvariants.com/44.dir/sankaku-shogi.html.