The Kieninger Trap is named after Georg Kieninger who used it in an offhand game against Godai at Vienna in 1925.Borik 1986, p.24 It occurs in the Rubinstein variation 3...Ng4 4.Bf4 with 4...Nc6 5.Nf3 Bb4+ 6.Nbd2 Qe7 7.a3. The Bb4 is attacked but Black does not have to move it for the moment, and instead both regains the gambit pawn and sets a with 7...Ngxe5 (see diagram). Superficially, White seems to win a piece with 8.axb4, but that would be falling into the Kieninger Trap because it would allow 8...Nd3 mate. ChessBase contains 76 games where White has lost this way; even after the exchange 8.Nxe5 Nxe5, the threat of ...Nd3 mate remains and indirectly defends the Bb4 from capture.
