Your king is under attack!

In our last chapter, we explored why the king has to be careful about which squares it uses. Now imagine your opponent moves a rook onto an open line pointing straight at your king. What happens next?

The king is in check. That means an opposing piece is attacking the square on which your king stands. It is a warning you must respond to — not the end of the game.

Look at the black rook on e8 and the white king on e4. Nothing blocks the rook's view down the e-file. White is in check and must deal with it on the very next move.

What exactly is check?

A player gives check by attacking the opponent's king. The king is never captured and taken off the board. Instead, the rules require the player under attack to make a move that leaves their king safe.

That means:

• You cannot ignore check, even if you see a tempting capture elsewhere.
• You cannot answer check with a move that leaves the king attacked.
• You must find a legal response. If none exists, it is checkmate — the subject of Chapter 9.

If you are the player giving check, you do not win a point simply for checking the king. You have created a threat that the opponent must answer.

Spot the checking piece

Remember the movement patterns from Foundations? They become useful again here. Rooks attack along ranks and files, bishops along diagonals, queens along both, knights jump in an L shape and pawns attack diagonally forwards.

Here is a bishop checking the white king along a diagonal:

The bishop on b7 follows c6–d5–e4 to the king. There isn't an intervening piece to break the attack.

Now compare that with a knight on f6:

The knight is checking the king on e4 without needing an open line. Remember: knights jump, so moving a piece somewhere between the knight and king doesn't stop its attack.

The queen can check along either a straight line or a diagonal, combining what we learnt about rooks and bishops. Here, the queen on b7 uses a diagonal to check the king on e4.

And a pawn can give check too. The black pawn on d5 attacks e4, not d4:

Try this: Before revealing the highlights, identify the attacking piece and name the square it attacks. Finding the source of the check is the first step towards escaping it.

Three ways to escape check

Once you've identified the attack, there are three possible kinds of response:

1. Move the king to a square that is not attacked.
2. Capture the checking piece, using the king or another friendly piece, if the capture makes the king safe.
3. Block the line of attack, by moving a friendly piece between the king and the attacker — when there is room to do so.

You might have one of these options, several of them, or only one legal move in the entire position. You only need to make one legal response, not all three.

Option one — Move the king

Let's return to the rook checking along the e-file. If the king simply steps from e4 to e3, it stays on the same attacked file. That isn't a legal escape.

Instead, White can move the king off the rook's line, provided the destination isn't attacked by anything else. On this board, d4 and f4 are examples of safe squares.

Option two — Capture the checking piece

Sometimes the best answer is to remove the attack entirely. Here the black knight on f6 checks the king on e4, but White's rook on f4 can capture the knight by moving to f6.

That is a legal response because the capture removes the checking piece and leaves the king safe. White can also find safe king moves, but capturing is an option worth noticing.

A warning: A checking piece isn't automatically safe for your king to capture. If it is defended, your king cannot move onto its square. In this example, a black rook protects the checking pawn on d5. White's king on e4 cannot capture that pawn.

Capturing another piece elsewhere on the board doesn't help unless it actually ends the check.

Option three — Block the attack

Some pieces check along a line. A rook uses a file or rank; a bishop uses a diagonal; a queen may use either. If there is an empty square between the checking piece and the king, you may be able to put a friendly piece on it.

In this position the black rook on e8 checks White's king on e4. White has a bishop on c3.

Moving the bishop from c3 to e5 places it between the rook and king. The rook attacks the bishop, but it no longer attacks the king through it. Blocking is a legal response. The bishop doesn't have to survive indefinitely; it just needs to stop the immediate check.

When blocking cannot help

Knight checks cannot be blocked. The knight doesn't travel along a line of squares between its starting point and the king; it jumps directly to the target.

A pawn checking diagonally from the next rank also leaves no square between itself and the king for you to block. The same is true of a rook, bishop or queen giving check from the very next square on its line.

You must then find another legal response: perhaps moving the king or capturing the attacker. In the knight position above, the bishop on c3 can actually capture the knight on f6 along its diagonal. That is capturing, not blocking — an important difference.

A simple routine when you're in check

You don't need to panic or calculate ten moves ahead. Try this routine:

1. Find the threat. Which piece is checking your king?
2. Look for safe king moves. Can you step away from all attacked squares?
3. Look for captures. Can the king or another piece safely take the attacker?
4. Look for blocks. Is there an attacking line you could interrupt?
5. Check the result. After your proposed move, is your king still attacked?

You won't always have all three kinds of escape. You'll also sometimes discover that several moves work, and choosing the best one is a separate question we'll return to later.

Have a go on the board

In this position, the rook is checking the king along the e-file and White's bishop has an opportunity to block. Try selecting the bishop on c3 and moving it to e5. You could also find a safe move for the king.

Check Escape Challenge

Time to put it together. You'll see four positions, each with a short list of candidate moves. Select every candidate that legally gets White out of check. Some suggestions are tempting but don't stop the threat.

Unlike our earlier Capture Challenges, you're not trying to take every piece. You're deciding which responses obey the rules. The exercise checks the actual position using chess rules, and tells you why a particular candidate is safe or unsafe.

What to remember

• Check means an opposing piece is attacking the king's square.
• The king is not captured. You must reply with a move that leaves your king safe.
• There are three kinds of response: move the king, capture the checker or block the attack.
• Blocking only works where there is an intervening square on an attacker's line. A knight's check cannot be blocked.
• A capture only works if it really ends the check; a defended piece may be impossible for the king to capture.
• Before you play your answer, check whether your king would still be attacked.
• If there is no legal move to escape check, that's checkmate — and it's what we'll explore next.

Knowledge check

Let's see whether you can recognise checks and find the right type of response.