Checking distance
Checking distance is the space a defending rook keeps from the enemy king, usually a long way off, so it can give a series of checks from the side or behind without being attacked.
A rook that checks from close range is easy to chase. The enemy king steps next to it, attacks it, or hides behind its own pawn, and the checks stop. A rook that stands far away can check again and again, and the king has no way to threaten it. That space between the checking rook and the king is the checking distance.
The idea matters most in rook and pawn endings, where the defender wants to harass the attacking king and its pawn. Placing the rook on the far side of the board, or far behind the pawn, gives many squares to check from. It is also why defenders prefer the long side of a pawn, since the rook there has more room to work.
In the example, the black rook is on h1 and the white king is on d4. The rook is far from the king, so it can give the check Rh4+ along the fourth rank, and nothing stands in the way. A rook next to the king would have far fewer such options.
A common mistake is to bring the rook close to the king to try to attack it or to defend a pawn, which gives up the checks. Another is to run out of safe checks and be left with a passive rook move that lets the king advance. When defending, keep the rook where it has room, and count how many safe checks you have before you commit.
Also worth reading is Frontal checks. Frontal checks are rook checks given from in front of the enemy king, facing the direction in which it is moving, as opposed to checks given from behind.
Compare it with Rook and pawn versus rook. Rook and pawn versus rook is the ending where one side has a rook and a single pawn against a lone rook, a common practical ending whose result usually turns on where the defending king stands.
Also worth reading is Vancura position. The Vancura position is a drawing setup against a rook pawn on the sixth rank with its rook in front: the defending rook attacks the pawn from the side, and the defending king waits on the far side of the board.
If "Checking distance" has cost you half a point, a first lesson is a good place to find the pattern behind it: George Li goes through your games and builds a plan.
Related terms
Frontal checks are rook checks given from in front of the enemy king, facing the direction in which it is moving, as opposed to checks given from behind.
The long side is the side of a pawn's file with more files between it and the edge of the board, giving a rook more room to check from far away.
The short side is the side of a pawn's file that has fewer files between it and the edge of the board, the opposite of the long side where more room is available.
Rook and pawn versus rook is the ending where one side has a rook and a single pawn against a lone rook, a common practical ending whose result usually turns on where the defending king stands.
A rook endgame is an ending in which each side has a rook and some pawns and no other pieces, and it is the most common type of endgame, so its main ideas are worth learning early.
An active rook controls open lines, attacks enemy pawns or the king from behind or the side, and cannot easily be attacked, which makes it far stronger than a rook that merely sits and defends.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
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