Battleship

Overview

Each player hides a fleet on a hidden grid and calls coordinates to sink the opponent's ships. A guessing game with genuine underlying strategy. Two players.

This entry is checked against Hasbro's current Battleship instructions, item A3264 (©2016).

1. Setup

Each player has two 10×10 grids, lettered A–J and numbered 1–10. One holds your fleet; the other tracks your shots.

Place five ships, horizontally or vertically, not diagonally, not overlapping:

Ship	Length
Carrier	5
Battleship	4
Destroyer	3
Submarine	3
Patrol Boat	2

Those are the names in the current set. Older sets called the 3-hole ship a cruiser and the 2-hole ship a destroyer, which is why the names get argued about.

The sheet's only placement rules are horizontal or vertical, never diagonal, and no part of a ship over the letters or numbers. It doesn't forbid ships touching; some house rules do.

2. Play

Players alternate calling a single coordinate: "D7."

The opponent must answer truthfully, "hit" or "miss", and on a hit they also tell you which ship you hit. Hasbro's own example:

You call: "D-4". Alex answers: "Hit. Destroyer".

When every hole in a ship has been hit, its owner announces which ship was sunk. Many people play without naming the ship on each hit. That makes the game harder, and the sheet offers it only as an option in the Salvo variant (below).

Mark hits and misses on your tracking grid.

3. Winning

Sink all five enemy ships.

The Salvo game

The sheet's own variant for experienced players:

• you fire one shot per ship still afloat, starting with five, and the opponent calls hit or miss after each;
• each ship you lose costs you one shot from your next salvo;
• for a harder game, don't announce which ships are hit.

4. Strategy

Far more than it appears.

Do not fire randomly. The shortest ship is two squares, so firing in a checkerboard pattern — every second square — is guaranteed to find every ship while using only half the shots. This alone dramatically outperforms random searching.

Hunt then target. Once you register a hit, fire at the four adjacent squares to establish the ship's orientation, then work along that line.

Probability density is the optimal method. For each square, count how many valid ship placements could cover it given what you know. Fire at the highest count. The centre of the board supports more placements than the edges, so early shots should favour the middle.

Place your own ships against this. Avoid the centre, avoid symmetry, and do not place ships flush against the edges in the obvious way — human opponents look there too.

A perfect game requires 17 shots, the total length of all five ships.

Knowing which ship you've hit, as the standard rules require, makes hunting much easier: you know how long it is, so you know when to stop following a line.

Commonly argued

• Ships cannot be placed diagonally.
• You say which ship was hit, on every hit, not just when it sinks.
• You must announce a sinking, and which ship it was.
• Nothing in the rules stops ships touching.
• The 3-hole ship is the destroyer and the 2-hole ship the patrol boat in the current set.
• The checkerboard pattern is strictly better than random, and most people never use it.