Three-movers

Directmate problems that require White to deliver mate by the third move are termed three-movers. In this type, White starts with the unique key-move, and after the black defences White proceeds with the second-move continuations. Usually, for each defence there is only one correct White continuation, which – whether by creating its own threat or setting up a block position – leads to mate on the third move. Compared with the two-movers introduced in the previous articles, three-move problems provide the capacity for more complex play and enable the rendition of certain themes that are otherwise not achievable.

Three-movers are broadly divided into the two schools of model-mate and strategic problems. The point of model-mate compositions lies in their variety of striking final mating positions, whereas strategic problems emphasise the interplay between the white and black forces. Problem 13 illustrates the first type, and begins with 1.Bc4! (waiting). 1…Kxh4 permits 2.Qf4+, which leads to two elegant mates that echo each other: 2…Kh5 3.Bf7, and 2…Kh3 3.Bf1. In these mating pictures, every square next to the black king is covered (i.e. guarded by White or blocked by Black) only once, resulting in what is called a pure mate. A model mate is defined as a pure mate that involves every available white piece, with the possible exception of White’s king and pawns. Two more model mates occur after 1…Kf5, in the lines 2.Qg3 Ke4 3.Bd3, and 2…Kf6 3.Qg5. Lastly, 1…Kh5 allows a short mate, 2.Qg5.

The scope for originality in model-mate problems is comparatively limited, and today the great majority of three-movers published are of the strategic variety. Problem 14 features a vintage strategic idea known as the Indian theme. Black has only one legal move in the diagram, 1…bxa2, which threatens stalemate. Set play is provided for this move, 1…bxa2 2.Bc2 Kxg2 3.Be4, where White avoids the stalemate by cutting off the second rank, and mates by opening this rank again by discovery. White has no first move capable of preserving this set variation, however, and the remarkable key is 1.Ba8! (waiting). Now 1…bxa2 produces analogous play on the long diagonal, 2.Rb7 Kxg2 3.Rb2. The three-move manoeuvre shown here – the Indian theme – consists of (1) White’s first move that crosses over a critical square (b7 in this case), (2) self-interference on that critical square to relieve stalemate, and (3) re-opening of the interfered line to discover mate.

The occurrence of multiple phases in a problem’s solution, oft-seen in two-movers, is not as prevalent in three-move problems. A three-mover’s extra length typically compensates for its having only one phase of play, in terms of how much content the work entails. Thus the previous problem is the only one in this small selection to incorporate changed play between two phases (set and actual play). Nonetheless, thematic tries – without necessarily introducing changed play – are an important part of many three-movers, such as Problem 15. The knight on d5 has three ways of threatening mate, and each fails to a defence by Black’s light-squared bishop, 1.Sc3? (threat: 2.Sa4) Be8!, 1.Se3? (2.Sc4) Bf7!, and 1.Sf4? (2.Sd3) Bg6! White’s bishop is suspiciously out-of-play, and the key indeed utilises this piece, with 1.Be1! bearing a short threat, 2.Bc3. Any move by Black’s knight would defend by opening the diagonal for the bishop on h8, but wherever the knight goes, it finds itself obstructing the movement of the other bishop. Hence 1…Se8 2.Sc3 for 3.Sa4, since 2…Be8 is prevented (and if 2…Bxc3+ 3.Bxc3). And 1…Se6 2.Se3 for 3.Sc4, since 2…Bf7 no longer guards c4. And 1…Sf5 2.Sf4 for 3.Sd3, since 2…Bg6 is now ineffective.

More fine strategic play is found in Problem 16. White wants to unpin the pawn on b6 to give mate on b7, but if 1.Rxa7+? Sxa7, the pawn mate is stopped by the black rook. White can try to move the king to unpin the pawn, but a series of black rook checks would refute, e.g. 1.Kd3? Rb3+! 2.Kc2 Rb2+. The key 1.Kf2! surprisingly leaves the pawn pinned and makes no threat. The black knight is immobilised because of 1…S-any 2.Rxa7. If Black moves the rook along the rank, then 2.Rxa7+ Sxa7 3.b7, or 1…Rf1+ 2.Kxf1 (3.b7) Sxd6 3.Rxa7. The thematic variations occur when the rook remains on the b-file. 1…Rb4 is met by 2.d4, which not only threatens 3.b7 but forestalls 2…Rf4+ as well, 2…S-any 3.Rxa7. 1…Rb3 is similarly answered by 2.e3, which has the same threat and also disables 2…Rf3+. And 1…Rb2 allows another delicate unpin of the white pawn by 2.Kg2, hiding the king again from further rook checks.

A three-mover is said to exhibit quiet play if, particularly in the main variations, White’s second moves are non-checking. Quiet play is generally considered favourably for being more subtle, but checking continuations by no means preclude excellent thematic play, as Problem 17 demonstrates. The difficult key 1.Kd7! threatens 2.Qd5+ exd5 3.e8=Q. Black defends three times by putting a major piece on d1, to control d5 from behind the white queen, but each time the black major piece has to relinquish its guard against a queen mate elsewhere. 1…Rbd1 2.Sbd3+ cxd3 or exd3 3.Qa5, 1…Qd1 2.Bd4+ Bxd4 3.Qxg5, and 1…Rhd1 2.Sfd3+ cxd3 or exd3 3.Qh2. White’s second moves in these variations show many matching effects. In each case, a white minor piece sacrifices itself on the d-file with check, unpinning the white queen, and also opens a line for the queen to access its mating square. By-play here includes 1…Sb6+ 2.Bxb6 (3.Bxc7) cxb6 3.Qd6, and a few short mates, 1…Qh7 2.Sg4, and 1…Bd4 2.Qxd4 or 2.Bxd4.