Characteristic 1 : The key sacrifices a very strong piece, especially on a square where more black pieces can take it.
”New York Saturday Courier”, 1855
White plays and mates in 3 moves
The white has a battery of forces aiming the black king. It seems that, if the knight leaves its square, the queen will threat the king. So, the solver might start to try such moves:
1.Sc2+? but the black king has a flight to f5 : 1...Kf5!
1.Sf5+? but the black king captures (symbol x) the knight on f5 : 1...Kxf5!
The move of the white, which is parried with a unique defense of the black, is called a try. The try is written with a question mark (?) and the unique defense is written with an exclamation mark (!). If tries exist, they make the solving harder and the problem more interesting.
In the problem-3 of the famous American composer Sam Loyd, (30/01/1841 – 10/04/1911), who published it when he was fourteen years old(!), there are five more tries with moves of the bishop:
1.Bh4? / Bd8? / Be7? but black has defense 1...f5!
1.Bg7? but the black king flights to g5 : 1...Kg5!
1.Bg5+? but the black king takes the bishop at g5 : 1...Kxg5!
In the solution white sacrifices a strong piece, (destroying the apparently threatening battery), achieving (first) a black pawn to change column and to self-block the black king, and (second) the bishop to have time to find support when moving to g5:
Key: 1.Qe6! fxe6 2.h4 e5 3.Bg5#
Characteristic 2 : The key allows black to develop more power by promoting his pawn.
Characteristic 3 : The key exposes the white king to check.
First prize "Checkmate", 1903
White plays and mates in 3 moves
Loyd composed in 1903 this chess problem with aim to have the most strange first move, the most improbable key, (having characteristics 2 and 3). He submitted the problem to a composition contest of the Canadian magazine "Checkmate" and he was awarded with the first prize.
For those who will try to study this problem, we give the hint that there are 13 tries:
1.Bb5-a4+? / Bb5-d3+? / Bb5xe8+? / Bb5-c6+? / d3? with defense 1...Kd4!
1.Rf6xf2+? / Rf6-f3+? / Rf6-f8+? / Rf6-f7+? / Bb5-e2+? / Bb5-c4+? / Bb5xa6+? with defense 1...Kxe4!
1.Rf6-f4+? with defense 1...Kxf4!
The solution of the problem is:
Key: 1.Ke2! (Black can now get a new queen by promoting f2, giving at the same time double check!)
1...f1=Q++ (but there is a hidden plan for white).
2.Ke3 (The king reaches e3, supports Se4, and is threatening d4 check, or discovered check by moving Bb5 or Rf6. Here black can give check from ten squares, but no check stays unanswered. See...)
2...Qf2+ 3.Rxf2# (The battery Bg7-Rf6 is activated) or
2...Re2+ 3.Bxe2# (The battery Ra5-Bb5 is activated) etc.
Indicatively, we present some more variations:
1...Sc1+ 2.Ke3 f1=S+ (underpromotion) 3.Rxf1#
1...Kxe4 2.Bd3+ Kd4 3.Rf4#
1...Bf4 2.Rf7+ Kxe4 3.Bd3#
1...f1=S+ 2.Rf2+ Kxe4 3.Bd3#
This problem has got the name Steinitz’s gambit, because the white king is moving just as he moves
in the opening of the OTB "Vienna game" : 1.e4 e5 2.Nc3
in the variation "Steinitz’s gambit" : 2...Nc6 3.f4 exf4 4.d4 Qh4+ 5.Ke2 .
1. Gambit : is the sacrifice of a pawn during the opening of the chess game.
2. The notation for chess games uses N for Knight, while the notation for chess compositions uses S for Knight, N for Nightrider).
[This Post in Greek language]