You have a dangerous passed pawn on the seventh rank (or on the second rank for a black pawn), one step away from promoting to a new queen - but the promotion square is blocked by a piece. In the following diagrams, you can see different ways of removing the blocker in order to promote your pawn:

In the first diagram, your own piece blocks the promotion square. The white rook can move out of the way of the pawn. The move indicated by the arrow achieves this with check, ensuring promotion on the next move: 1.Rd8+ Kc7 2.a8=Q. This is called clearance.

In the second diagram, the opponent's piece blocks the promotion square. The rook can give check to force the black king away. By attacking the blocker, the rook also guards the promotion square, so the pawn can promote safely on the next move: 1.Rd8+ Kc7 2.b8=Q+.

In this level, we are practising attacking the blocker.

Examples

White has a dangerous protected passed pawn on h7. The promotion square is blocked by Black's king on h8. White can attack the blocker with 1.Nf7+. After the forced reply 1...Kg7, White can now promote with 2.h8=Q+. The new queen cannot be captured by the king, because attacking the blocker also has the advantage of protecting the promotion square. Therefore White can keep the new queen and will checkmate soon.

Sometimes attacking the blocker of a promotion square is worth a sacrifice, as in the following example:

Black has a passed pawn on g2, which is protected by the rook on g8. Black can't promote immediately, because White's king on g1 is blocking the pawn. Black can sacrifice a bishop and win by attacking the blocker with 1...Bxf2+! After the forced reply 2.Kxf2, Black can promote to a queen with 2...g1=Q+. White cannot capture the queen, because it is protected by the rook on g8, therefore Black has a winning material advantage.

Sometimes attacking the blocker can include other motifs:

White has a dangerous passed pawn on c7, which is blocked by Black's rook on c8. Black just attacked White's rook with Kf7-e8, but that was a mistake. White can win with the surprising 1.Rd8+, attacking the blocker. Now if 1...Kf7, White wins with 2.Rxh8 Rxh8 3.c8=Q. And if 1...Rxd8 White promotes with 2.c8=Q, and if Black captures the new queen with 2...Rxc8, White wins the rook on h8 with the skewer 3.Rxc8+.

Related combinations

There are various ways to remove the defence. In addition to attacking the blocker, other ways to remove the defence include deflection and capturing the defender.