Porthole Chess Rules

Porthole Chess Rules

Porthole chess – an awesome Chess variant
Get ready for a new strategy game with all the elements of chess plus all the excitement of portholes. Chess puritans won’t like it, but they don’t like any variants. Everyone else will probably agree that this is the best addition to chess, ever.

To play porthole chess all you need are round disks. Quarters work well, but poker chips or any suitable token may be used. Place 8 of them on the board as shown in Figure 1.


Figure 1.  A Porthole Chess board setup.  Use quarters or poker chips or some such as portholes.  You may place as many or as few as you like, though the default is to play with 8. It seems to be a good balance.


All you need to know:

Think of a porthole as a dynamic, neutral chess piece that either player can use to their advantage on their turn. A porthole can be activated by any valid capture move. For example, a pawn can enter a porthole by traveling diagonally one space, landing on the porthole. The queen may enter any porthole that she can legally travel to horizontally, vertically, or diagonally.
A porthole move is composed of entering and exiting a porthole. A piece enters one porthole, and exits at another. An entry porthole can be either occupied (by an enemy piece) or it may be open. The exit porthole must be open. The entry porthole moves to the square where the player piece was before the move began. Figure 2 shows an example of such a porthole move.
Figure 2.  In step 0, it is white's turn. Ordinarily, this would be a checkmate situation.  In step 1, white moves the King onto an open, and in this case, vacant, entry porthole.  In step 2, the King has traveled to an exit porthole (white selects which open porthole to use as an exit.)  In step 3, the entry porthole moves to where the King was when the move was initiated.  Now it is black's turn.
It is important to note that a player can not attack another player piece through a porthole. To put it another way, you cannot enter one porthole and come out on another porthole and take the piece that is there. The exit porthole must be unoccupied. All occupied portholes are considered blocked during the exit phase of the move.
A player can attack an enemy piece that is on a desired entry porthole. The enemy piece is captured and the move is completed normally (meaning the porthole token goes to the originating square, and the piece exits to a desired unoccupied porthole.) The fact that an enemy piece was captured in the process is a bonus. Figure 3 shows such a move.
Figure 3.  In step 0, it is white's turn.  White's pawn is feeling threatened by black's pawn.  In step 1, white's pawn makes a valid "capture move" against black's pawn, who happens to be sitting on a porthole.  In step 2, white's pawn finishes the move by landing on an open porthole, and the entry porthole has moved to white's original position.

In other words, porthole behavior is the same whether occupied or open. The difference, and the power, is that an opposing piece is taken, and you move out of harm’s way all in one turn.  You can think of portholes as “attack activated” because a pawn will be blocked from moving vertically onto a porthole, but the pawn may enter the porthole as a diagonal attack. This is also shown in Figure 3.

What is clear to see is not always clear to explain, thus terms are used to help explain what is easier to see. Use the terms to help you remember if a move is valid or not, and look for the anomalies that can occur and use them to your advantage (if you can!)



Porthole Chess Terminology


Porthole States: (Open, Occupied, Active, Dormant, Stoned)

  • Open: Porthole is not occupied and free for entry and exit.
  • Occupied: A porthole is occupied when a piece is on that porthole. You cannot exit through an occupied porthole, and a porthole does not become open until the end of the move, so no fair returning to the porthole that you entered
  • Active: A porthole is made active by any valid capture move against an open or occupied porthole. The active porthole is then placed on the square where the capturing piece was before the move was initiated.
  • Dormant:  A dormant porthole is a porthole that is covered, or occupied, by one or more portholes. You cannot enter, or exit from, a dormant porthole.
  • Stoned:  A stoned porthole may sound like a drugged state, but it is an anomaly that occurs when all but one porthole is occupied. A porthole is stoned when there are no open portholes except one. The last open porthole appears to be open to enter, as there is nothing on it. However, since there is no exit, there is no legal move involving the porthole, thus it is stoned, and you may not enter a stoned porthole. As soon as another porthole is open, the stoned state goes away.
Porthole Characteristics: (blocking, neutrality, dynamic)
  • Blocking: You cannot move over a porthole. In this respect, think of a porthole as another piece on the board. The normal concepts of blocking or shielding apply here. Just as the bishop (for example) cannot pass over a pawn to accost a third piece, the porthole cannot be passed over.
  • Dynamic: A porthole move involves three squares on the board: the location of the players piece before the move begins, the entering porthole, and the exiting porthole. The players piece ends on the exiting porthole, the entering porthole ends up were the piece was before the move began. Because portholes are attack activated, pawns have to move diagonally through portholes and cannot move forward through them. Any valid capture move against a porthole, whether an opponent’s piece is on the porthole or not, will result in a porthole move.
  • Neutrality: Though you are sometimes asked to think of a porthole as another piece, they have no allegiance, and no aggressive abilities.


Tips and things to think about:  

Portholes can give the king a great advantage. The porthole can be used to block and make quick exits -- if you have good porthole control.
Queens are as powerful as ever, but pawn advancement is now a real possibility, even in the early part of the game. Look for ways to sacrifice a queen for positional advantage.
Portholes allow rooks another way out onto the board. Castling is still valid, but remember you can't castle over a porthole. A porthole is like any other piece on the chess board in that respect.
The porthole gives the bishop the power to change its color, a kind of religious conversion! Thus bishops can now back each other up.


A porthole prevents forward motion of a pawn, just as if the pawn was blocked by any other piece. Pawns must use an attacking motion to activate a porthole. The pawn may “attack” the porthole whether there is an enemy piece there or not. Because portholes allow pawns to move to any open porthole, a pawn can end up back where they started.  This does not mean you can move that pawn forward two spaces on your next turn. That is reserved for a pawns first move!
Pawn Advancement:
If a pawn advances to the last rank, they can be promoted as usual. Portholes can speed this up tremendously. However, if they are on the last rank on a porthole, they are not promoted, because the porthole is neutral territory. So, a pawn must move from the 7th to the 8th rank as the last step before promotion. If a pawn ends up on the last rank on a porthole, the pawn is stranded waiting to die, because there are no valid moves for the pawn to make, but there are valid moves to be made against the pawn. The stranded pawn does serve the purpose of locking one of the portholes, which in itself is useful.
It should also be noted hear that En-passant is not a valid move in porthole chess. 


General Observations

It has been said that porthole chess is simply regular chess with portholes added. From the surface it might seem almost trivial addition to the game. It is not. If you’re a good chess player you will feel like a beginner again, but only for a little while, because the abstraction comes easy. Just as in standard chess, your ability to analyze a chess board will be critical.  Thus, even an experienced porthole chess player is no match for a skilled chess player.

  • You can't defend a piece on a porthole.
  • Pinning a piece with check or mate is more difficult. (recall Figure 2)
  • Rooks are not just for the end game anymore.
  • Pawn Advancement is a threat early in the game.
  • Multiple Queens is a realistic possibility and not just the result of poor game play.
  • Pawns can “go backwards” via a porthole, but cannot repeat the “two spaces” move.
  • Kings can be more active.
  • Kings and portholes go together.
  • You can't defend a piece on a porthole. Try it!
  • Pinning a piece with check is more difficult.
  • Rooks are not just for the end game anymore.
  • You really, really can't defend a piece on a porthole.


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