The game Battleship is a guessing game played by two people. Although made popular throughout the world as a commercial board game, first published by the Milton Bradley Company in 1931, it was originally played as a pencil and paper game.

Description
The game is played on two square grids, one for each player. The grids are typically square, and the individual squares in the grid are identified by letter and number. On one grid the player arranges his own ships and records the shots by the opponent. On the other grid, the player records his own shots.

Before play begins, each player arranges a number of ships secretly on the grid for that player. Each ship occupies a number of contiguous squares on the grid, arranged either horizontally or vertically. The number of squares for each ship are determined by the type of the ship. The ships cannot overlap (i.e., at most one ship can occupy any given square in the grid). The types and numbers of ships allowed are the same for each player. These may vary depending on the rules. A typical arrangement would be:

1 aircraft carrier (5 squares)
1 battleship (4 squares)
1 destroyer (3 squares)
2 cruisers (2 squares each)
1 submarine (1 square)
Another arrangement would be:

1 aircraft carrier (5 squares)
1 battleship (4 squares)
1 destroyer (3 squares)
1 submarine (3 squares)
1 cruiser (2 squares) 
After the ships have been positioned, the game proceeds in a series of rounds. In each round, each player has a turn. During a turn, the player announces a list of target squares in the opponents' grid which are to be shot at. If a ship occupies one of the squares, then it takes a hit. When all of the squares of a ship have been hit, the ship is sunk. After the target list has been given, the opponent then announces which of his ships have been hit. If at the end of a round all of one player's ships have been sunk, the game ends and the other player wins. If all of both players ships are sunk, the game ends in a tie.

The number of target squares that a player may shoot at in a given turn is determined by the condition of the players' own ships at the beginning of the round. The player is allowed to target one square for each square in his own ships which are not sunk. Thus with the ships described above, the players would have 17 shots in the first round. As each ship is sunk, the player losing that ship loses the corresponding number of shots. Thus with the ships described above, if the battleship is sunk, the player loses 4 shots.


Battleships with ships
A commercial version which sticks to its namesake is played on a 10 by 10 rectangular grid with these vessels: 1. Carrier (5 squares x 1 square) 2. Battleship (4 x 1) 3. Cruiser (3 x 1) 4. Submarine (3 x 1) 5. Destroyer (2 x 1)

When all the squares of a vessel is hit, its owner declares its name and that it has been sunk. The player who sinks all of his or her opponent's vessels first wins. The normal gameplay allows an additional shot to be fired after each successful hit. (This makes it possible, if rare, for an player to win before their opponent can take a single action.) Some variants allow each player to fire as many shots as he or she has vessels afloat in each turn, instead of the single shot or shoot-till-you miss style turn.


Variations
Many variations in the basic rules are possible, including the sizes of the grids, the numbers and sizes of the ships, the numbers of shots allowed, and when hits are announced. Most of the variants simplify the game, which is useful for younger players.

In one variant, the opponent announces a hit after each target square is given. This reduces the challenge of guessing the locations of the ships.

In another variant, the number of shots allowed is reduced by each individual hit, rather than by ships sunk. This reduces the benefit for locating ships precisely.

A logical variation of battleship in which guessing is not required is more common in puzzle magazines. There will be some form of clues, either as row or column tallies or neighboring ship segment tallies in such a way that no guesses are needed to solve the puzzle. See Battleship (puzzle).