The square no pawn can take back

Almost every piece you develop gets chased by a pawn sooner or later. A piece on an outpost never does, because the pawn that would chase it does not exist any more.

Also called a strong square
Best occupied by a knight
Test can any enemy pawn ever attack it

An outpost is a square in or near your opponent's half of the board that no enemy pawn can attack. Not a square that is unattacked right now. A square where the pawns that would do the attacking have been traded off, or have already walked past it and cannot come back.

Working out whether a square is an outpost is arithmetic, not judgement. Name the square. Name the two squares an enemy pawn would have to stand on to attack it. Then check whether either pawn still exists and can still get there. Pawns do not move backwards, so the answer is often a flat no, and the moment it is, that square is yours for the rest of the game.

The knight on d5 in the Sveshnikov

White's knight has landed on d5 and has eight legal moves, none of which it needs to play. The pawns that could attack it would have to reach c6 or e6.

Black's c-pawn was traded on move three. Black's e-pawn is already sitting on e5, in front of the square it would need to occupy. Neither can ever come back, and no other black pawn can reach c6 or e6 without White first putting a piece on e6 for the f7 pawn to take. So the knight is not strong for the next ten moves. It is strong permanently, and Black spends the game trying to trade it or to prove that the wrecked kingside pawns matter more.

How to build one, in three steps

First, find the square. Look for a hole in your opponent's structure on the fourth, fifth or sixth rank, usually next to a backward pawn or in front of a half-open file. Then control it: a pawn supporting it from c4 or e4, a rook behind it, a bishop covering it. Only then move a piece in, because a knight that arrives before the square is supported gets traded on arrival and you have gained nothing.

Then defend the square from the pieces that fight for it. This is the step people skip. If your opponent has a bishop covering d5, the outpost is not an outpost yet, and trading that bishop is worth more than the pawn you were about to grab somewhere else.

The knight is the best piece for an outpost, because it is the piece that gains most from never having to move.
An outpost on the sixth rank is worth roughly a pawn on its own. On the fifth it is a long-term advantage. On the fourth it is just a good square.
Supported by a pawn is best. If the outpost is defended only by pieces, your opponent can pile up on it and win the exchange of attackers.
The far side of a pawn chain is the first place to look, because the pawns that could have guarded those squares are the ones that advanced.

Questions people ask

What is the best piece for an outpost?

A knight, almost always. A knight on a secure square in the middle of the board attacks up to eight squares and cannot be hit by anything cheaper than itself, and unlike a bishop or a rook it does not need open lines to be useful. A bishop on an outpost is fine but rarely needs one, because a bishop can do its work from your own half of the board.

What is the difference between an outpost and a weak square?

They are the same square seen from opposite sides. A weak square is one you can no longer defend with a pawn; an outpost is that square once your opponent has a piece heading for it. A hole only becomes an outpost if the other player can actually occupy and hold it, which is why counting weak squares in a position is less useful than asking which one a knight can reach.

Outpost sits under Pieces and squares in the reference. Nearby: