# Four Towers

Four Towers is a fairly complex but still chesslike variant. It's played on an 85-square board that is rotationally but not bilaterally symmetrical. The board is basically 9x9, being made up of nine 3x3 zones called "arenas." It also includes four "tower" squares. The empty board is shown in Figure 1. For most purposes, the board is a single continuous surface, and the movement of pieces within and between arenas and onto, off of, and across towers takes place exactly as you'd expect. The layout become significant in certain situations, however. Depending on which pieces are situated on the tower squares, certain types of moves may become available or unavailable to other pieces.

Figure 1. The board in Four Towers. The tower squares are marked in the ASCII diagram with the letter 'T'. Six of the nine 3x3 arenas are highlighted with attractive but meaningless symbols to help you visualize the layout. (Indicating the boundaries of the arenas is not easy with ASCII graphics.) Note that each tower square borders four arenas. The center arena is bordered by all four towers. The four towers are not part of any arena. The question which are the white squares and which the black ones is arbitrary; I'd suggest making the towers white squares, so that the corners are black.

```        +---+---+---+
| . | . | . |                         11
+---+---+---+---+---+---+
| . | . | . |   |   |   |             10
+---+---+---+---+---+---+---+---+---+
| . | . | . |   |   |   | # | # | # |  9
+---+---+---+---+---+---+---+---+---+---+
|   |   |   | T |   |   |   | # | # | # |  8
+---+---+---+---+---+---+---+---+---+---+
|   |   |   | * | * | * | T | # | # | # |  7
+---+---+---+---+---+---+---+---+---+---+
|   |   |   | * | * | * | ' | ' | ' |      6
+---+---+---+---+---+---+---+---+---+---+
| = | = | = | T | * | * | * | ' | ' | ' |      5
+---+---+---+---+---+---+---+---+---+---+
| = | = | = | : | : | : | T | ' | ' | ' |      4
+---+---+---+---+---+---+---+---+---+---+
| = | = | = | : | : | : |   |   |   |          3
+---+---+---+---+---+---+---+---+---+
| : | : | : |   |   |   |          2
+---+---+---+---+---+---+
|   |   |   |          1
+---+---+---+
a   b   c   d   e   f   g   h   i   j   k
```

For purposes of description, the arenas are indicated with Roman numerals, in the arrangement shown below. As with conventional letters and numbers to indicate squares, the numerals are always shown with reference to the white player's side of the board. That is, the arena that includes squares a3 through a5, b3 through b5, and c3 through c5 is always referred to as arena I.

```VII   VIII  IX
IV    V     VI
I     II    III
```

Each player begins the game with the usual complement of chess pieces, with the following additions: a marshall and a cardinal (familiar from numerous chess variants), two dragons, and two extra pawns. The opening layout is shown in Figure 2.

Figure 2. The opening layout in Four Towers. The tower squares, which are unoccupied at the beginning of the game, are marked 'T' in the ASCII diagram. White pieces are shown as capital letters, and black pieces as lower-case letters.

```     _ _ _
|d|m|k|_ _ _       11
|r|n|b|d|c|q|_ _ _ 10
_|p|p|p|p|p|p|b|n|r| 9
|_|_|_|T|_|_|p|p|p|p| 8
|_|_|_|_|_|_|T|_|_|_| 7
_|_|_|_|_|_|_|_|_|_|   6
|_|_|_|T|_|_|_|_|_|_|   5
|P|P|P|P|_|_|T|_|_|_|   4
|R|N|B|P|P|P|P|P|P|     3
|Q|C|D|B|N|R|     2
|K|M|D|     1

a b c d e f g h i j k
```

## Movement of Pieces

With the exception of the pawns, the familiar pieces move and capture in the expected manner. The movement of pawns is slightly enhanced: in addition to moving forward and capturing on the forward diagonals, they can move (but not capture) exactly one square sideways. After a two-square initial forward move, a pawn can be captured en passant. There is no castling. Pawns promote to any other piece (except a king) on reaching the last square in any file that was occupied by enemy pieces at the beginning of the game -- files c through k for the white pawns, and files a through i for the black pawns. One of the reasons for allowing pawns to move sideways is to allow each player's two leftmost pawns to reach squares where they can promote.

Any pawn that is on a square where one of the pawns of its side started the game can make a two-square advance, whether or not it has moved previously. (This convenient rule means that when looking at a board diagram, you don't need to know the history of the game to know whether a pawn can make a two-square move.) A pawn that has gotten positioned behind the starting pawn position for its side can also make a two-square advance.

The marshall moves like either a rook or a knight. The cardinal moves like either a bishop or a knight.

During the course of the game, two other types of pieces -- wizards and lancers -- can appear on the board. A wizard combines the moves of rook, bishop, and knight, making it the most powerful piece in the game. The lancer is a move powerful member of the pawn class. It can make a capturing or non-capturing move of one or two squares straight forward or on the forward diagonal. It can also make a non-capturing move of one or two squares to the left or right. A lancer can never back up. It doesn't leap; the first square must be vacant for it to make a two-square move. A lancer promotes like a pawn on reaching the other side of the board. Lancers and pawns can capture one another en passant. A lancer can be captured en passant, either by another lancer or by a pawn, any time it makes a two-square move that crosses the square threatened by the enemy pawn or lancer. A couple of examples of en passant capture are shown in Figure 3.

Figure 3. Pawns and lancers can capture one another en passant, any time one of them makes a two-square move that crosses a square where capture is possible. Here, the white lancer on g5 can capture the black pawn on i8 if the pawn makes a two-square advance to i6 (marked 'x'). The lancer captures to i7 (marked 'o'). In the same way, if the white lancer on e5 makes a two-square move to c7 (marked 'x'), it can be captured en passant by the black lancer on f6, which captures to d6 (marked 'o'). Finally, consider the opposing lancers on d9 and g9. If either of them moves two squares sideways toward the other, the moving lancer can be captured by its opposite number either in the normal way or en passant.

```     _ _ _
|_|_|_|_ _ _        11
|_|_|_|_|_|_|_ _ _  10
_|_|L|_|_|l|_|_|_|_|  9
|_|_|_|T|_|_|_|p|_|_|  8
|_|x|_|_|_|_|T|o|_|_|  7
_|_|_|o|_|l|_|_|x|_|    6
|_|_|_|T|L|_|L|_|_|_|    5
|_|_|_|_|_|_|T|_|_|_|    4
|_|_|_|_|_|_|_|_|_|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

The movement of the dragons will be explained below, following the discussion of attachment and detachment.

## Attaching and Detaching

In Four Towers, the three major pieces each player with which each player starts the game (queen, marshall, cardinal) are compound pieces. That is, they don't simply move like a combination of rook/bishop, rook/knight, or bishop/knight respectively. Each of them is in fact a fusion of those two pieces, rather in the way that a hydrogen atom consists of a proton fused with an electron. In the same way, a wizard consists of a fused rook, bishop, and knight.

At any point in the game, pieces that are fused together can separate. Or, conversely, two friendly pieces of appropriate type can fuse to create a new compound piece. A move in which two pieces combine is called an attachment move, and a move in which two pieces split apart is called a detachment move. Only pairs of pieces from the same army can attach to one another; attaching to enemy pieces is not allowed.

An attachment or detachment move is made in place of an ordinary move, and requires a turn. An attachment move operates rather like a piece capturing a friendly piece. For instance, a white knight can move onto a square occupied by a white rook. Both are removed from the board, and a marshall is placed on the square formerly occupied by the rook. In all cases, the moving piece must make a legal move of its normal type.

To continue the example, at this point the marshall moves, captures, and can be captured as a single piece. Later in the game, however, the player may move either the knight or the rook individually, leaving the other piece behind. This is a detachment move. At this point, the marshall is retired from the board, either the knight or the rook is put on the square formerly occupied by the marshall, and the rook or knight is moved to its new square. Again, the moving piece must use a normal, legal move for a piece of its type.

A detachment move may be used to capture an enemy piece. Attachment and detachment can take place on tower squares.

The marshall has been used above by way of example. The same process can occur with the cardinal, queen, or wizard. A wizard can be created in an attachment move by combining a marshall and a bishop, a cardinal and a rook, or a queen and a knight. Any of these pieces can later be detached from the wizard. Several possible attachment and detachment moves are shown in Figure 4.

A compound piece that already contains a simple piece of a given type can't be combined with another piece of that same type. For instance, you can't attach a knight to a cardinal, because a cardinal already contains a knight.

A moment's thought will show that each player's starting complement of pieces can be detached into four rooks, four bishops, and four knights. (We're ignoring the king, dragons, and pawns for the moment.) Conversely, the forces can be fused into four wizards.

A lancer is a pair of fused pawns. To create a lancer, one pawn is moved onto the square of another friendly pawn, using either a capturing or non-capturing type of pawn move. The detachment move, in which the lancer is turned back into two pawns, must be made in a manner appropriate to the pawn that is moving. That is, if the pawn moves forward or to the side, it must be a non-capturing move, but if it moves forward on the diagonal, it must be a capturing move. If the lancer is on a square where a pawn starts the game, the detachment move can be two squares forward.

Two compound pieces can never attach to one another. A detachment move can also be an attachment move, however, as Figure 4 illustrates. For example, a knight could detach from a marshall (leaving a rook on the square where the move began) and, moving in a normal knight-move, land on the square of a friendly queen, creating a wizard. Likewise, a pawn can detach from a lancer and immediately attach to another pawn to make a new lancer.

The possibility of fusing pawns with other pieces is intriguing, but this concept is not implemented in Four Towers. Nor can dragons or the king be fused with any other piece.

Figure 4a. An artificial position showing how the pieces stand before various attachment and detachment moves are made.

```     _ _ _
|_|_|_|_ _ _        11
|n|_|_|r|_|_|_ _ _  10
_|_|_|_|_|_|_|c|_|_|  9
|_|_|_|T|_|_|_|_|_|_|  8
|_|_|_|_|_|_|T|_|_|_|  7
_|_|_|_|P|L|_|_|_|_|    6
|_|W|_|T|_|_|_|Q|_|_|    5
|_|_|_|_|_|_|T|_|_|_|    4
|_|_|_|_|_|_|M|_|_|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

Figure 4b. The same forces as in Figure 4a, after various attachment and detachment moves have taken place. The rook on f10 has attached to the knight on c10, creating a marshall. The bishop portion of the cardinal on i9 has detached, moving to g7 and leaving a knight behind. A cardinal has detached from the wizard on b5, moving like a knight to a3. The knight portion of the marshall on g3 has detached and immediately reattached to the queen on h5, creating a new wizard. In the same fashion, one of the two pawns in the lancer on f6 has detached and attached to the pawn on e6.

```     _ _ _
|_|_|_|_ _ _        11
|M|_|_|_|_|_|_ _ _  10
_|_|_|_|_|_|_|n|_|_|  9
|_|_|_|T|_|_|_|_|_|_|  8
|_|_|_|_|_|b|T|_|_|_|  7
_|_|_|_|L|P|_|_|_|_|    6
|_|R|_|T|_|_|_|W|_|_|    5
|_|_|_|_|_|_|T|_|_|_|    4
|C|_|_|_|_|_|R|_|_|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

Tactical Considerations. Attachment moves add to the pieces' mobility. In effect, by attaching a bishop to a rook to make a queen, you can ferry either piece to another spot on the board, a spot that it could reach alone only with greater difficulty (or, in the case of the bishops, perhaps not at all). Attaching also allows the two portions of a fused piece to attack different enemy pieces from the same square. Detachment is especially useful when a compound piece is in a position to capture an enemy piece. By detaching the capturing piece, you can give your opponent less material to retake. Also worth noting: You should never promote a lancer, though it's legal to do so. By detaching one of the two pawns, you gain the opportunity for two promotions.

## The Dragons

The dragons have no defined type of movement of their own. Instead, a dragon moves in a manner determined by the recent moves of other pieces.

The dragon takes on the movement and capture powers of the pieces (except for pawns, lancers, and other dragons) moved most recently by both players. For instance, if white has just moved a knight and black a rook, all of the dragons now have the ability to move like either a knight or a rook. Recent moves by dragons, pawns, and lancers are ignored in figuring out how the dragons move. If a player moves pawns for five turns in a row, for instance, the dragons continue to mimic the move of whatever piece that player moved before the pawn moves.

If one of the most recent piece moves was by a compound piece (queen, marshall, cardinal, or wizard), the dragon acquires all of the possible movement vectors of that piece. It's not limited by the move actually used by the piece. For instance, when a marshall is moved, the dragons can move in either a rooklike or a knightlike manner, because the marshall is capable of both types of movement.

Note that if an enemy dragon is on the same row, file, or diagonal as your king (or a knight's move from it), it may be illegal for certain of your pieces to move, because to do so would put your king in check. This is called a dragon pin.

In an attachment or detachment move, the piece that moves is the one whose move the dragon copies. For instance, if a bishop moves onto a square occupied by a rook to make a queen, the dragons acquire the ability to move like bishops (not queens).

## The Towers

When a piece is moved onto a tower, its presence has an effect on the four arenas touching the tower. This effect remains in force for as long as the piece is on the tower, and ends when it is removed. Each type of piece has its own effect. In arenas that adjoin two (or, in the case of arena V, four) towers, two or more pieces may be creating effects at the same time. There are also special rules covering how pieces leave the towers.

Some of the effects created by putting pieces on towers may seem odd or hard to remember, but they were chosen for a reason. My goal was to create effects that were interesting and well balanced, but not so dramatic that the business of getting pieces on the towers and keeping them there or knocking them off would completely dominate the game. For instance, a rule to the effect that whenever a rook was on a tower, all friendly pawns would be able to move like rooks would turn every game into a mad scramble to put your own rooks on the towers and get enemy rooks off of them.

When a marshall is on a tower, friendly and enemy rooks, knights, and marshalls (but not other compound pieces that include rooks and knights) become rather like a separate universe. They can neither capture other pieces, nor be captured by other pieces, though they can continue to capture one another. They can't capture other pieces when their move either starts or ends on a square in any of the four arenas touching the tower, and they can't be captured while in any of these arenas -- except, as already noted, by one another. In addition, because an attachment move is like a capture, rooks, knights, and marshalls can't make or be the target of attachment moves that start or end in any of these four arenas if a diagonal-moving piece is involved. Knights can still attach to rooks or vice-versa, but knights can't attach to queens or bishops, for example. Nor can knights or rooks be detached from compound pieces other than marshalls when the compound piece is situated in any of the four arenas touching the marshall's tower.

When a cardinal is on a tower, all of the knights and bishops (but no compound pieces) within the four arenas touching the tower switch their movement ability: Knights move and capture like bishops, and bishops move and capture like knights. This applies only to knights and bishops whose moves start in any of the four arenas, not to knights and bishops that move into one of the four arenas from elsewhere on the board. Dragons become confused by this switch: They mimic the type of movement the knight or bishop has actually made, not its usual movement.

When a queen is on a tower, her king becomes invulnerable to check in the four adjacent arenas. The king can move into check freely within any of these arenas, and a check need not be removed for as long as the queen remains on the tower. If the king would be in check, of course, it's illegal to move the queen off of the tower, and any enemy move that removes the queen from the tower is a check.

When a wizard is on a tower, the player whose wizard it is gains the ability to make rearrangement moves in any of the four arenas adjacent to the tower. A rearrangement move is made instead of an ordinary move in a turn. In a rearrangement move, any or all of the pieces belonging to the player within a given arena can be freely repositioned on new squares within the same arena. Only one arena can be rearranged per turn, and enemy pieces cannot be rearranged. The pieces must be moved to vacant squares within the arena: Rearrangement can't be used to capture enemy pieces. Because the rearrangement does not use the pieces' normal movement type(s), it is ignored when figuring out which moves the dragons can currently mimic, even if only one piece has been rearranged.

When a king begins his move on a tower, he can capture like a queen, moving any number of squares orthogonally or diagonally in a straight line. If he leaves the tower with a non-capturing move, however, he moves normally.

When a pawn is on a tower, both friendly and enemy pawns in the four adjacent arenas can make double-square advances, just as if they hadn't moved yet. When doing so, they can be captured en passant by lancers and other pawns.

When a lancer is on a tower, all of the pawns and lancers in the four adjacent arenas, both friendly and enemy, gain the ability to make a non-capturing move of exactly one square backward.

When a dragon is on a tower, the player whose dragon it is can make non-capturing moves with, in a single turn, up to four pieces. Each of the four pieces must start its move in one of the four arenas touching the tower, and each must start its move in a different arena. A multiple piece move is only allowed if none of the moves are capturing moves. (In other words, if the player makes a capturing move, no multiple move is allowed in that turn.) Unlike a rearrangement move, which can also involve multiple pieces, in this type of multi-piece move all of the pieces use their normal, legal type of movement. There is no restriction on what arenas the pieces' moves may end in. If a piece's move starts in one of the arenas adjacent to the dragon's tower and ends in another such arena, it can be moved again as part of the same multi-move. Figure 5 shows an extreme example of this.

When several pieces are moved simultaneously in a multi-piece move, all of the dragons on the board gain the ability, in the following move, to move like any of the pieces just moved. Also worth noting: The player making a multi-piece move can move the various pieces in any order. One may need to be moved in order to unblock another. One of the moves in a multi-piece move may leave the player's own king in check, provided it is not in check after all of the pieces being moved are moved. The enemy king can be checked multiple times, or for that matter checkmated, in a multi-piece move.

The player's other dragon may not participate in a multi-piece move made possible by a dragon on a tower. (Dragons may participate in rearrangement moves, however.)

Figure 5. The dragon on the h8 tower allows the knight on g5 to move four times, ending its move on f10. This move is possible because the intermediate squares (which must be vacant) are all in different arenas.

```     _ _ _
|_|_|_|_ _ _        11
|_|_|_|x|_|_|_ _ _  10
_|_|_|_|_|_|.|_|_|_|  9
|_|_|_|T|_|_|_|_|.|_|  8
|_|_|_|_|_|_|d|_|_|_|  7
_|_|_|_|_|_|_|_|.|_|    6
|_|_|_|T|_|_|n|_|_|_|    5
|_|_|_|_|_|_|T|_|_|_|    4
|_|_|_|_|_|_|_|_|_|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

When a rook is on a tower, all of the pieces, both friendly and enemy (including pawns), in the four adjacent arenas gain the ability to make non-capturing moves to analogous squares in adjacent arenas to the left, right, forward, or back of their present arena. The square being moved to must either be vacant or occupied by a friendly piece to which the moving piece can attach. Such a "direct move" must be non-capturing. Figure 6 should make the idea clear. Only one such direct move can be made per turn; this is not a multi-piece move.

Figure 6. With the rook on the d5 tower, the queen on e4 gains the ability to move directly to f7 or b5 (marked in the ASCII diagram with 'x') because arena I is to the left of arena II, and arena V is above arena II. However, the queen can't move to c8 (marked 'o'), because the relationship between arenas II (where the queen is situated) and IV is diagonal. The queen can't move to h3 (also marked 'o') because it isn't one of the four arenas touching the rook's tower.

```     _ _ _
|_|_|_|_ _ _        11
|_|_|_|_|_|_|_ _ _  10
_|_|_|_|_|_|_|_|_|_|  9
|_|o|_|T|_|_|_|_|_|_|  8
|_|_|_|_|x|_|T|_|_|_|  7
_|_|_|_|_|_|_|_|_|_|    6
|_|x|_|R|_|_|_|_|_|_|    5
|_|_|_|_|Q|_|T|_|_|_|    4
|_|_|_|_|_|_|_|o|_|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

When the rook is on the d5 tower, as shown in the figure, direct moves can be made to analogous squares in other arenas in the following ways:

```I  <-> II
IV <-> V
I  <-> IV
II <-> V

```

The geometric relationship of arenas affected by a rook on a tower is similar if it's on one of the other three towers.

The effect of a bishop on a tower is similar to the effect of a rook, but pieces can move directly to analogous vacant squares (or squares occupied by attachable friendly pieces) in arenas that are in a diagonal rather than an orthogonal relationship with respect to the tower. In this case, the queen in Figure 6 would be able to move directly to c8, but not to b5 or f7. With a bishop on d5, arenas I and V become connected in this manner, as do arenas II and IV.

When a pair of rooks or a pair of bishops, or a rook and a bishop, are on towers, all of the pieces in the affected arenas can move "through" vacant squares in other arenas and continue in whatever manner is allowed in those arenas, all within a single move. For an example of what can occur, see Figure 7.

It's not possible to check the enemy king by moving a rook or bishop onto a tower so as to create the possibility of such a direct arena move, because the direct move must be non-capturing.

Tactical Considerations. Putting a rook or bishop on one of the towers adjacent to one's opening position provides a quick way to develop pieces. During the opening, the danger of having the enemy's center pawns be moved directly into one's own ranks is not great, as they'll be easy to capture. Later in the game, one will be better off trying to establish a rook or bishop on one of the enemy's towers. Putting a rook or bishop on a tower also makes it easier to make attachment and detachment moves.

Figure 7. The white pawn on b5 can move directly to f7, the analogous square in arena V, because of the white bishop on the d5 tower. It can then continue to g10 because of the presence of the black rook on e8, which makes possible direct moves between arenas V and VIII. Yes, this pawn may seem to be in an innocuous position, but it's about to be promoted.

```     _ _ _
|_|_|_|_ _ _        11
|_|_|_|_|x|_|_ _ _  10
_|_|_|_|_|_|_|_|_|_|  9
|_|_|_|r|_|_|_|_|_|_|  8
|_|_|_|_|o|_|T|_|_|_|  7
_|_|_|_|_|_|_|_|_|_|    6
|_|P|_|B|_|_|_|_|_|_|    5
|_|_|_|_|_|_|T|_|_|_|    4
|_|_|_|_|_|_|_|_|_|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

The effect of a knight on a tower is to change the way pieces that move orthogonally (vertically and horizontally) move from one of the four adjacent arenas to another. It's as if the four arenas are lined up perfectly rather than offset from one another -- as if the tower square has disappeared. Diagonally moving pieces and pieces moving like knights are not affected, but pawns and lancers are affected when moving orthogonally. This has some peculiar results, as Figures 8, 9, and 10 show.

Figure 8. The path of a rook is refracted when it moves from one arena to another if a knight is on a tower that overlooks both arenas. Here the path of the rook on e3 is refracted (to the squares marked with dots) when it moves from arena II to I or from II to V, because of the knight on d5, and again when it moves from V to VIII because of the enemy knight on h7. The path from II to III is not affected, because there is no knight on g4. A queen, marshall, wizard, or dragon will be affected in exactly the same way when moving in an orthogonal direction, but not when moving diagonally or like a knight.

```     _ _ _
|_|_|_|_ _ _        11
|_|_|_|_|.|_|_ _ _  10
_|_|_|_|_|.|_|_|_|_|  9
|_|_|_|T|_|.|_|_|_|_|  8
|_|_|_|_|.|_|n|_|_|_|  7
_|_|_|_|_|.|_|_|_|_|    6
|_|_|_|N|_|.|_|_|_|_|    5
|.|.|.|_|.|_|T|_|_|_|    4
|_|_|_|.|R|.|.|.|.|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

Figure 9. Because of the knight on the g4 tower, the pawn on f4 can either capture or advance in a non-capturing move to g5 (marked '!') as it crosses the boundary from arena II to arena V. It can also capture at e5 (marked 'x'), but can't advance to g5 until the knight leaves the tower. The king on i4 can move or capture at h3 (marked '*') using (redundantly) either its vertical or diagonal type of movement, but it can't move to i3, because the move to i3 is refracted to h3.

```     _ _ _
|_|_|_|_ _ _        11
|_|_|_|_|_|_|_ _ _  10
_|_|_|_|_|_|_|_|_|_|  9
|_|_|_|T|_|_|_|_|_|_|  8
|_|_|_|_|_|_|T|_|_|_|  7
_|_|_|_|_|_|_|_|_|_|    6
|_|_|_|T|x|_|!|_|_|_|    5
|_|_|_|_|_|P|N|_|K|_|    4
|_|_|_|_|_|_|_|*|_|      3
|_|_|_|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

Figure 10. When a knight is on a tower, it can't be captured by pieces that move vertically or horizontally. Here, the black rook on g5 can't attack either of the white knights on towers, because its vertical and horizontal moves are refracted to the squares marked with dots.

```     _ _ _
|_|_|_|_ _ _        11
|_|_|_|_|_|_|_ _ _  10
_|_|_|_|_|_|_|_|_|_|  9
|_|_|_|T|_|_|_|_|_|_|  8
|_|_|_|_|_|_|T|_|_|_|  7
_|.|.|.|_|_|_|_|_|_|    6
|_|_|_|N|.|.|r|_|_|_|    5
|_|_|_|_|_|.|N|_|_|_|    4
|_|_|_|_|_|.|_|_|_|      3
|_|_|.|_|_|_|      2
|_|_|_|      1

a b c d e f g h i j k

```

Pieces can leave a tower square in any of three ways: by a normal capturing or non-capturing move (just as if the tower were an ordinary square), by being captured, or by being swapped. Attachment and detachment moves can also occur on towers.

### Tower Swap.

A swap move can occur in two reciprocal ways, which are illustrated in Figure 11. First, a player who has a piece on a tower can move another piece (using the latter piece's normal, legal move) onto the same tower. The piece that is on the tower before the move is then placed on the square where the other piece started its move. In effect, they have traded places. The second type of swap is similar, but it's the piece on the tower that makes a legal move of its type, ending the move on a square occupied by a friendly piece. The latter piece is then moved onto the tower.

A pawn can be swapped onto or off of a tower only by using the movement of the other piece; it can't initiate a swap. Note that a knight can't be swapped off of a tower by a rook or by any other piece moving as a rook, because rooks can't reach the tower squares.

Figure 11. The knight on i4 can be swapped with the bishop on e8 (because e8 is a tower) using the bishop's move. The knight on b4 can swap places with the rook on d5 (also a tower) using the knight's move.

```     _ _ _
|_|_|_|_ _ _       11
|_|_|_|_|_|_|_ _ _ 10
_|_|_|_|_|_|_|_|_|_| 9
|_|_|_|B|_|_|_|_|_|_| 8
|_|_|_|_|_|_|T|_|_|_| 7
_|_|_|_|_|_|_|_|_|_|   6
|_|_|_|R|_|_|_|_|_|_|   5
|_|N|_|_|_|_|T|_|N|_|   4
|_|_|_|_|_|_|_|_|_|     3
|_|_|_|_|_|_|     2
|_|_|_|     1

a b c d e f g h i j k

```

### Capturing a Piece on a Tower.

When a piece moves onto a tower square that is occupied by an enemy piece, the result is not necessarily a capture. The player whose piece is removed from the tower by the capturing-type move has two options: Accept that the piece was captured and make a normal move, or return the captured piece to the board. It can be returned to the board by being placed on any vacant square in any of the four surrounding arenas. Returning the piece to the board requires a turn -- that is, it's done instead of moving a piece. Returning the piece to the board must be done in the move immediately following its capture: The piece can't be held in reserve and returned to play later.

The piece returned to the board may be placed in a position where it gives check to the enemy king. The return is considered a move by the piece in reckoning the current powers of the dragons.

It may seem that returning a captured piece to play is always a better choice than losing it -- but remember, when the enemy piece moves onto the tower, the tactical situation on the board is likely to change. It may be necessary to answer some new threat, or take advantage of some new opportunity, rather than returning the captured piece to play.

If you'd care to play a game of Four Towers by email, please feel free to wander over to the Contributors page, where the author's email address is located.

Written by Jim Aikin. Rules of Four Towers (c) 2001 Jim Aikin.
WWW page created: June 21, 2001. ﻿