Battleship · Complete guide
Battleship: how to play, and how to search like a computer
Hide a fleet, call your shots, and learn how much better a good search is than a lucky one — about fifty shots a game.
Battleship is a search problem dressed as a naval battle. Each player hides five ships on a 10×10 grid — seventeen squares in total — and the two take turns calling coordinates until one fleet is gone.
It began as a pencil-and-paper game in early twentieth-century Europe, spread among soldiers in the First World War, and is still played on squared paper in Russia as Morskoi Boi. The familiar plastic version with the pegs and the hinged case came from Milton Bradley in 1967.
What makes it worth thinking about is how much strategy is available in a game that looks like pure guessing. Random shooting takes about 95 shots to clear a fleet. Hunt and target — random until a hit, then work outwards — takes about 65. Adding parity, firing only at every second square because the smallest ship covers two, gets you to about 50. And computing a full probability density — which squares are covered by the most possible remaining ship placements — reaches about 40.
Deployment matters too, and mostly in the opposite direction from instinct: the centre of the board is up to eight times more likely to hold a ship than a corner, which tells you both where to shoot and where to hide.
How to play
The grids, the five ships, how shots and hits are called, when to announce a sunk ship, and the variants worth knowing — including the one rule everybody argues about.
Where it comes from
A pencil-and-paper game played in the trenches, commercialised as Salvo in 1931, turned into plastic by Milton Bradley in 1967 — and now a textbook example of how to search efficiently.
- Battleship began as a pencil-and-paper game in early twentieth-century Europe with no known inventor.
- It spread widely among soldiers in the First World War, and is still played on paper in Russia as Morskoi Boi.
- Salvo, published in the United States in 1931, was among the first commercial versions.
- Milton Bradley's plastic edition arrived in 1967; Electronic Battleship followed in 1977.
How to win
Why random shooting takes 95 shots and good search takes 40: parity hunting, hunt-and-target, probability density maps, and how to deploy a fleet that is genuinely hard to find.
- Random shooting needs about 95 shots; parity plus targeting takes about 50; probability density about 40.
- While hunting, fire only at every second square — every ship must cover one.
- After a hit, fire at the four neighbours; after two in a line, fire at the ends only.
- Central squares are up to eight times more likely to hold a ship than corners — shoot there, hide elsewhere.
Common questions
How many ships are in Battleship?
Five per player, covering 17 squares: one of length 5, one of 4, two of 3 and one of 2. The 1990 and 2002 editions use different names for the same sizes.
Can ships touch each other?
In the official rules, yes. Many players use a house rule forbidding it, which makes the deduction game richer. Agree before you deploy.
What is parity in Battleship?
Firing only at squares of one colour of a checkerboard. Since the smallest ship covers two adjacent squares, it must touch one of them — so half the board is enough to find every ship.
Where should I hide my ships?
Away from the centre, spread apart, not touching, and not in the same pattern every game. The centre is covered by far more possible placements, so that is where good opponents search first.
How many shots does it take to win?
About 40 with probability-based play, 50 with parity and targeting, and roughly 95 shooting at random.
Guides
Play Battleship free, right now
No sign-up, no download — it runs in your browser against the computer, a friend on the same device, or a friend online.