Threat correction

A move of the white thematic piece introduces the initial threat, but also introduces a general error which Black can use to defeat.
No other move by white thematic piece can prevent that defence by providing a mate in reply to it.
So instead of correcting the general error it corrects the actual threat.
For the sake of completeness, the initial threat should recur after some other defence.

Szwedowski, Leopold
Wola Gułowska, 1989
3rd Prize

mate in 2 moves

FEN: 5B2/2p2P2/2p5/1p2k3/1P2p2K/2pbp2N/Q1N5/3R1R2