- White makes the only move that forces checkmate in the stipulated number of moves.
- Black's defences include the promotion of a certain pawn, to either a knight, a bishop, a rook, or a queen. (Black may have other defences as well.)
- If Black promotes, then White must promote a pawn to the same piece that Black just promoted to - this is the only way to force checkmate within the stipulated number of moves.
The task is named after the first person to speculate about the existence of such a chess problem, Joseph Ney Babson, in 1884. It is regarded as one of the greatest challenges for a composer of chess problems to devise a satisfying Babson task problem, and for around half a century it was unknown whether the task was possible.
The Babson task is a special form of Allumwandlung, a chess problem in which the solution contains promotions to each of the four possible pieces. Such problems were already known when Babson formulated his task.
|This article uses algebraic notation to describe chess moves.|
Forerunners of the Babson task
This 1912 problem by Wolfgang Pauly is, as it were, a three-quarter Babson task—three of Black's promotions are matched by White. White to move and mate in four:
The key is 1.b3, after which there are the following lines:
- 1...a1=Q 2.f8=Q Qxb2 3.Qa8 Qxc1 4.Qf3#
- 1...a1=R 2.f8=R (2.f8=Q? a2 3.Qf6 stalemate) a2 3.Rf6 Kxh4 4.Rh6#
- 1...a1=N 2.f8=N a2 3.Ng6 Nxb3 4.Nf4#
This is not a full Babson, however, because 1...a1=B 2.f8=B does not work – White must instead play 2.f8=Q, with similar play to above.
The earliest Babson tasks are all in the form of a selfmate – this is where White, moving first, must force Black to mate him against his will within a specified number of moves. In 1914, Babson himself published a selfmate which achieved the task, although three different white pawns shared the promotions. The first problem in which a single black and single white pawn were involved in the promotions was by Henry Wald Bettmann, and won 1st prize in the Babson Task Tourney 1925–26.
The key move in Bettmann's problem (left) is 1.a8=B, after which the play goes:
- 1...fxg1=Q 2.f8=Q Qxf1/Qxc5 3.b5 Qxb5#; or 2...Q-any 3.anyxQ Rxa6#
- 1...fxg1=R 2.f8=R R-any 3.anyxR Rxa6#
- 1...fxg1=B 2.f8=B B-any 3.anyxB Rxa6#
- 1...fxg1=N 2.f8=N N-any 3.anyxN Rxa6#
A number of other selfmate Babson tasks with one pawn of each colour doing all the promotions followed this one.
Composing a Babson task problem in directmate form (where White moves first, and must checkmate Black against any defence within a stipulated number of moves) was thought so difficult that very little effort was put into solving it until the 1960s, when Pierre Drumare began his work on the problem which occupied him for the next twenty years or so. He managed to compose a Babson task problem using nightriders (a fairy piece which moves like a knight, but can make any number of knight-like moves in the same direction in one go) instead of knights, but found it hard to devise one using normal pieces – because of their limited range, it is difficult to justify White promoting to a knight because of Black promoting to one way over the other side of the board.
When Drumare did eventually succeed using conventional pieces in 1980, the result was regarded as highly unsatisfactory, even by Drumare himself. It is a mate in five (first published Memorial Seneca, 1980):
The key is 1.Rf2, after which Black captures on b1 are answered by white captures on g8.
Efficiency in chess problems is considered a great boon, but Drumare's attempt is very inefficient—no less than 30 men are on the board. It also has six promoted pieces in the initial position (even a single promoted piece is considered something of a "cheat" in chess problems), which is in any case illegal—it could not be reached in the course of a game (one of the white f-pawns must have made a capture, and the white and black b- and c-pawns must have made four captures between them, making five in total, yet only two units are missing from the board). Despite all these flaws, it is the first complete Babson task.
In 1982, two years after composing this problem, Drumare gave up, saying that the Babson task would never be satisfactorily solved.
The following year, Leonid Yarosh, a football coach from Kazan then virtually unknown as a problem composer, came up with a much better Babson task problem than Drumare's – the position is legal, it is much simpler than Drumare's problem, and there are no promoted pieces on board. First published in March 1983 in the famous Russian chess magazine Shakhmaty v SSSR, this is generally thought of as the first satisfactory solution of the Babson task. Drumare himself had high praise for the problem. It is a mate in four:
The key is 1.Rxh4, and the main lines are:
- 1...cxb1=Q 2.axb8=Q Qxb2 (2...Qe4 3.Qxf4 Qxf4 4.Rxf4#) 3.Qb3 Qc3 4.Qxc3#
- 1...cxb1=R 2.axb8=R Rxb2 3.Rb3 Kxc4 4.Rxf4#
- 1...cxb1=B 2.axb8=B Be4 3.Bxf4 Bxh1 4.Be3#
- 1...cxb1=N 2.axb8=N Nxd2 3.Nc6+ Kc3 4.Rc1#
Black has more options for its first move, of course, but these are not part of the Babson theme. They also result in checkmate on the fourth move.
However, Yarosh's problem has a small flaw – the key is a capture, something which is generally frowned upon in problems. Also, when first presented the black piece at h4 was a pawn, but a computer discovered an additional solution by 1.axb8=N in that construction which is not there when a knight is substituted on that square. Nevertheless, when Dutch author Tim Krabbé saw this version in the Soviet publication 64, he records that the realisation that somebody had at last solved the Babson task had the effect upon him as if he had "... opened a newspaper and seen the headline 'Purpose Of Life Discovered'."
Yarosh continued to work on the problem and in August 1983 his improved version with a non-capturing key appeared in Shakhmaty v SSSR. It is generally considered one of the greatest chess problems ever composed. Again, mate in four:
The key here is non-capturing and also thematic (that is, it is logically related to the rest of the solution): 1.a7. The variations are largely the same as in the original:
- 1...axb1=Q 2.axb8=Q Qxb2 (2...Qe4 3.Qxf4 Qxf4 4.Rxf4#) 3.Qxb3 Qc3 4.Qbxc3#
- 1...axb1=R 2.axb8=R Rxb2 3.Rxb3 Kxc4 4.Qa4#
- 1...axb1=B 2.axb8=B Be4 3.Bxf4 Bxa8 4.Be3#
- 1...axb1=N 2.axb8=N Nxd2 3.Qc1 Ne4 4.Nc6#
Yarosh composed a completely different Babson task problem later in 1983 and another in 1986. Several other Babsons have since been composed by other authors.
The cyclic Babson
In the August 2003 issue of the German problem magazine Die Schwalbe, the problem to the right, a mate in four by Peter Hoffmann appeared. Hoffmann had previously published a number of conventional directmate Babsons, but this one is significant as it is the first cyclic Babson: rather than black promotions being matched by White, they are related in cyclic form: Black promoting to a queen means White must promote to a bishop, Black promoting to a bishop means White must promote to a rook, Black promoting to a rook means White must promote to a knight, and Black promoting to a knight means White must promote to a queen.
The key is 1.Nxe6, threatening 2.hxg8=Q and 3.Qf7#. The thematic defences are:
- 1...d1=Q 2.hxg8=B (2.hxg8=Q? Qd7+ 3.Bxd7 stalemate), threatening 3.c4+ Q-moves 4.BxQ#
- 2...Qd7+ 3.Bxd7 Kxg6 4.Rxh6#
- 2...Qxc1 3.Rxg5 (threat: 4.Rf5#) hxg5 4.Qh8#
- 1...d1=B 2.hxg8=R (2.hxg8=Q? stalemate) Kxe6 3.Rd8 3.Kf6 Rd6#
- 1...d1=R 2.hxg8=N (2.hxg8=Q? Rd4+ 3.c4 stalemate) Kxe6 3.Qxe2+ K-moves 4.Qe5#
- 1...d1=N 2.hxg8=Q Nxb2+ 3.Kb5(Bxb2) and 4.Qf7#
There are also a number of sidelines.
As with Drumare's original Babson task, the problem uses promoted pieces and has a capturing key, but it is nonetheless remarkable for being the first published cyclic Babson.
In the September 2005 issue of Schach, the first cyclic Babson without promoted pieces in the initial position was published. Again, the composer was Peter Hoffmann.
The key is 1.Nxb6. The thematic defences are:
- 1...d1=Q 2.exf8=B (2.exf8=Q? Qd4+ 3.Bxd4 stalemate; 2.exf8=N? Kd6 3.Be5+ Kc5 and no mate)
- 2...Qd4+ 3.exd4 Kxf6 4.d5#
- 1...d1=B 2.exf8=R (2.exf8=Q? stalemate; 2.exf8=N+? Kd6 3.Be5+ Kc5 and no mate)
- 2...Kd6 3.Qd2+ with mate after any move by black
- 1...d1=R 2.exf8=N+ (2.exf8=Q? Rd4+ 3.Bxd4 stalemate; 2.exf8=B? Rd7 3.c8=Q(B) stalemate)
- 2...Kd6 3.Be5+ Kc5 4.Qxc2#
- 1...d1=N 2.exf8=Q (2.exf8=N+? Kd6 3.Be5+ Kc5 and no mate)
- 2...Nxc3+ 3.Kxa5 Ne4 4.c8=Q#
- Tim Krabbé. "De man die de Babson task maakte" (in Dutch).
- Howard, Kenneth S., The Enjoyment of Chess Problems, Dover Publications, 1961, p. 213.
- Hooper, David; Whyld, Kenneth (1992). "Babson Task". The Oxford Companion to Chess (2nd ed.). Oxford University Press. ISBN 0-19-280049-3.
- Krabbé, Tim (1986). De man die de Babson task wilde maken. Nova Zembla. ISBN 9070711117.
- Jeremy Morse, Chess Problems Tasks and Records (Faber and Faber, 1995, revised edition 2001) – contains a chapter on the Babson task
- Peter Hoffmann. "100 Years: Babson Task in the Orthodox Directmate" (PDF).
- Tim Krabbé. "The Babson task". (a detailed analysis of Yarosh's second Babson)
- Tim Krabbé. "Sons of Babson". (lists Babsons published later)
- Tim Krabbé. "Hoe de Babson task orthodox werd" (in Dutch). (mentions two forerunners of the Babson task)
- Zalmen Kornin. "Babson-Task: A Key, And Beyond".