White has opened with four straight pawn moves, and now wins a piece with 5.Ke2! Really.
This comes from that most entertaining writer on chess, Tim Krabbé, and is currently republished at ChessCafe.com from their archives, a piece called "The Man Who Almost Played 5.Ke2," which first appeared in March 2000. It's a fascinating article you'll want to read (link at end of this post).
Although the first game Krabbé came across with this line was played in 1983, when he went looking for similar games with this theme (he turned up over 30), the earliest game he found was played by, who else, E. J. Diemer. Here's the story from Krabbé:
I had never seen the five-move version of this theme when I published the following BDG in 1983, coincidentally the same year the first game discoverd by Krabbé was played:"Interesting are those cases where Ke2 or Kf2 only seemingly win a piece, or where the choice between the king moves matters. The oldest game where this came up is from 1947:
Diemer – Kopp, Endingen 1947
1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 Bf5 5.g4 Bg6 6.g5 Nd5 7.Nxe4 e6 8.c4 Bb4+
This was the premiere of the standard position in one line of the Blackmar-Diemer Gambit, and it gets a diagram in Diemer’s classic Vom ersten Zug an auf MATT! 9.Kf2 Simply 9.Bd2 is probably best, as neither this king move nor 9.Ke2 wins a piece: 9.Ke2? Nb6 10.c5 Nd5 11.a3 Ba5 12.b4 Bxe4 13.fxe4? Nc3+ The game went 9...Nb6 10.c5? Bxe4 11.fxe4 Bxc5, and Black had saved his piece and won a pawn. This did not keep Diemer from winning the game in his special way: 12.Be3 Be7 13.Nf3 h6 14.g6 Bh4+ 15.Ke2 fxg6 16.Bh3 Qf6 17.Qb3 O-O 18.Bxe6+ Kh7 19.Raf1 Qe7 20.Nxh4 Re8 21.Nxg6 Kxg6 22.Bf5+ Kh5 23.Bg5 Qxg5 24.Qf3+ Kh4 25.Qh3 mate
In a sub-line however, White does win the piece:
Brunold – Strasser, Kempten 1988
1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 Bf5 5.g4 Bc8 6.g5 Nd5 7.Nxe4 e6 8.c4 Bb4+
9.Ke2 9.Kf2 does not work here; 9…Ne7 10.a3 Bd6 11.c5 Be5! 12.Be3 f5 and Black has saved his piece (13.Nc3 f4!) 9...Ne7 10.a3 Bd6 11.c5 and White won."
Kampars,N - Wehrley,OMJ
BDG, Vienna Defense
1.d4 Nf6 2.f3 d5 3.e4 dxe4 4.Nc3 Bf5 5.g4 Bg6 6.g5 Nd5 7.Nxe4 e6 8.c4 Nb6
In my notes to this game in the August 1983 issue of BDG WORLD I wrote this:
"Diemer, Harding, and Studier all warn that 8...Bb4 drops a piece to 9.Kf2, but offer no evidence. I'm skeptical, since it appears that Black can escape any immediate trap on his bishop at b4 with a timely exchange of his other bishop. This may be the early stages of amaurosis schacchistica on my part (I'm reluctant to go against two BDG masters and the other fellow), so I'd be grateful to any reader who can demonstrate the forced win of a Black piece after 8...Bb4 9.Kf2. In any case, the Bishop check is not recommended. 8...Ne7, as played in Tartakower- Simonovic (Paris 1954, 1:0, 59). drew a (!) from Diemer, but in view of his generosity with aurufzeichen, that could be considered damning with faint praise."
[Here's the line I had in mind at the time: 8...Bb4+ 9.Kf2 Nb6 10.c5 Bxe4 11.fxe4 Bxc5
9.Be3 N8d7 10.h4 Bb4+ 11.Kf2 0-0 12.c5 Nd5 13.a3 Nxe3 14.Kxe3 Bxe4 15.fxe4 Bxc5 16.dxc5 Qe7 17.Rc1 f5 18.Qc2 f4+ 19.Kf2 Ne5 20.Nf3 Ng4+ 21.Kg1 Ne3 22.Qb3 Rad8 23.Bh3 Rfe8 24.Rh2 Kh8 25.Qxb7 e5 26.Qb3 Rb8 27.Qc3 c6 28.b4 h5 29.Rd2 Ng4 30.Rd6 Rbc8 31.Rcd1 Rc7 32.Qd2 Kh7 33.Rd7 Rxd7 34.Qxd7 a5 35.Qxe7 Rxe7 36.Rd6 axb4 37.axb4 Ra7? 38.g6+ Kh6 39.Ng5 Ra1+ 40.Bf1 Ne3?? 41.Nf7# 1-0
which is actually Diemer-Kopp, above, but with which I was unfamiliar at the time. Diemer actually gives 9.Kf2 a (?) in his note to that game in his book, so I'm not sure where I picked up his verdict that it deserved a !--perhaps in one of his early letters or in his Blackmar Gemeinde, or maybe I just imagined it???]
Great fun. Play through the games here. Read Tim Krabbé's article here.