Legend of the day #6: White to play and win

Legend of the day · #6

The last knight of the gambit

Rudolf Spielmann vs Baldur Honlinger · Vienna 1929 · White to play, mate in 4

free · no wallet

White to play. Mate in 4.

Your move

Find the move Rudolf Spielmann found. The other side answers by itself.

The game

Rudolf Spielmann vs Baldur Honlinger

Vienna, 1929