Special moves
Underpromotion
Promoting to a knight, rook or bishop instead of a queen — on purpose.
What is the underpromotion?
Underpromotion is choosing a knight, rook or bishop rather than the obvious queen when a pawn reaches the eighth rank. Rare, but when it is right nothing else works: usually a knight to give an immediate fork or check, or a rook to dodge stalemate.
Why the underpromotion matters
It is the connoisseur's tactic. Underpromotions are uncommon enough that they slip past both players and even strong engines' intuition, and a single knight-promotion-with-check has saved or won many a famous study and game.
How to use it to win
Reach for it in two situations: when a new queen would give stalemate (promote to a rook to keep the win), and when a knight on the promotion square delivers a check or fork a queen could not. Always ask, "would a knight do something special here?"
Try an example puzzle
A real underpromotion puzzle from the app. White to move — find the idea, then reveal the line.
7 
2 Show solution
1. b8=R#
Drill the underpromotion on thousands of real puzzles, matched to your rating.