Exposed king

An exposed king is a king without pawn cover: stuck in the centre after castling was lost, or behind pawns that advanced or were traded away. It is not a tactic in itself but a condition. Against a covered king, a check is a move like any other; against an exposed one, every check comes with tempo, and a tempo is what every other tactic needs.

What makes it work is that a check restricts the reply to a handful of moves, so the attacker calculates a narrow tree and the defender walks it. The checks that win are the ones that also do something: a check that attacks a loose piece (a fork with check), a check that drives the king toward your other pieces, a check that forces a block you can take next move. A check that only checks is a wasted tempo.

To spot the chance, count the squares the king has and the lines that lead to it: open files, open diagonals, and your pieces that can reach them in one move. Two pieces reaching an exposed king usually decide it: two rooks on the seventh and eighth, a queen and a knight, a queen and a bishop on the long diagonal.

At higher level, forcing the king out is the first half of the combination. A sacrifice on f7, h7 or g7 costs a piece and buys a naked king; it is sound when your other pieces are already pointing at it. And the exposed king often hides behind one defender: the combination starts by removing it, then the checks do the rest.