Breakthrough is a race game. Its object is to first get a man onto the opponent's back row. Apart from the opponent, the wall is the most important obstacle in this quest.
The diagram shows the board and the pieces in the initial position. Players move in turn. White moves first.

The object of the game is to be the first player to get a man onto the opponent's back row. However, blocking the opponent completely also constitutes a win.

In turn, each player moves one of his pieces any number of squares diagonally, either forward or backward, with these restrictions:

initial position
  • A piece may not jump over another piece.
  • A piece may not move onto a square occupied by an opponent's piece.
  • When moving forward, a piece must stop if it reaches a square of the wall on the opponent's side of the board. Once on the far wall, a piece may not move forward from it except by explosion.
    A piece may move backward from or backward across the wall. The wall on a player's own side of the board does not affect the movement of his pieces.
  • A piece may move onto a square already occupied by one of his own pieces. Thus stacks may arise.
    Such a stack moves as a unit, following all rules and restrictions of single men, and 'explodes' if it's height surpasses the square's 'capacity'.
  • Moving is compulsory.

  • Each square in the central three columns will hold at most two men.
  • Each square in the side columns will hold at most one man.

If a move results in a square exceeding its capacity, the square explodes, which means that it shoots its men to the adjacent squares in forward and sideways directions.
  • For the central columns this means one man forward, one to the left and one to the right.
  • For the side columns it means one man forward and one sideways.
  • The remainder, if any, stays on the original square.

Men dispersed by an explosion ignore the second and third restriction listed above under movement. Thus an explosion may require a piece to be dispersed onto a square occupied by an opponent's piece. This piece, whether a single man or a pair, is captured and removed from play. There is one important exception:
  • A piece on the far wall is safe from capture: any opponent's man that explodes onto its square is instead eliminated itself.

explosions explosions explosions
Chain reactions
If an explosion and the resulting dispersal of men causes other squares to surpass capacity, these all explode as part of the same turn. The order in which to perform them is up to the player.
An example can be given right from the start: if white opens with 1.b2a1, this causes a1 to surpass capacity, dispersing its contents to b1 and a2. The latter therewith also surpasses its capacity and in turn explodes its men to b2 and a3.
All has settled down in the rightmost diagram. This is not at all an unusual opening move.

Strategy is fairly obvious: you need an explosion from the far wall to get beyond. Side columns explode fastest, so a7 and e7 appear obvious targets for white to get his men on.
The drawback of this strategy is that, if successful, it gets a man across on the sidecolumn on a8 or e8, where a defender can block it with a single man on b9 or d9. If however the attacker next successfully targets the same square again by a second explosion from the same square on the wall he wins because this would cause the square on the eighth row to explode.

Breakthrough © MindSports

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