In response to a certain black defence, White makes a mating move in the actual play that is surprisingly different from that in another phase, such as set play and try play, against the same defence.

This concept of changed play is intensified in the zagoruiko theme, which specifies a framework of changed variations.  A two-mover demonstrates the Zagoruiko scheme if the following occurs: at least two black defences lead to changed white mates, with each defence provoking at least three different white mates in separate phases.

The theme is named after a Russian composer who devised some notable examples in the 1950s.

The try 1.Rc6? (waiting) provides for 1…Kd5 with 2.Qf3, and 1…Kd3 with 2.Qf5, but is defeated by 1…d3!.  A second try, 1.Nba3? (waiting), reverses the two queen mates against the same defences: 1…Kd5 2.Qf5 and 1…Kd3 2.Qf3, but 1…d3! again refutes.  Such a reversal of white mates across two phases constitutes the reciprocal change theme.

This additional effect is cleverly brought about by the try-pieces guarding and un-guarding different squares along the c-file.

74. Miklós Locker
64 1971
Special Prize

Mate in 2

75. Valentin Lukianov
64 1981
2nd Prize

Mate in 2

The play of 75 revolves around two prominent captures by Black’s d5-pawn.  1.axb3? covers c4 and threatens 2.Qe3, and either black pawn capture would defend by creating a flight on d5: 1…dxc4 2.Qxc4 and 1…dxe4 2.Qd1; but the pinning 1…Ra2! defeats the try.

1.Kf3? covers e4 and threatens 2.Be3, and now 1…dxc4 Qd1 and 1…dxe4+ 2.Qxe4; but another pinning defence refutes, 1…Rf7!

Correct is 1.e6!, which threatens 2.Be5 and significantly opens a white rook’s line to d5.  The resulting variations are 1…dxc4 2.Qe3 and 1…dxe4 2.Be3.

Notice an interesting paradox that further connects the tries and actual play.  Earlier, the try 1.axb3? carried the threat of 2.Qe3, against which 1…dxc4 was a defence.

Problem 76 involves one more phase than the previous examples, generating a 4x2 Zagoruiko.  Black’s main defences are 1…Ne2 and 1…Nh3, both of which cause a weakness by cutting off a black rook’s line.  White exploits each of these interferences in four different ways.

The set play is 1…Ne2 2.Be6 and 1…Nh3 2.Bxh7.  When White moves the knight away from f4 to threaten 2.Rf4, the white bishop is left alone to control e6, so it can no longer give the set mates.

The try 1.Ne6? obstructs the black pawn and attacks g5, enabling 1…Ne2 2.Ra5 and 1…Nh3 2.Qxh7, but Black refutes by 1…Rxe6!

Another try 1.Ng2? changes the play again, to 1…Ne2 2.N2e3 and 1…Nh3 2.Nh4, and is answered by 1…Rxg2!

76. Horacio Musante
British Chess Magazine 1956
1st Prize

Mate in 2

77. Gerhard Maleika
Echecs Francais 1981
1st Prize

Mate in 2

Problem 77 features a complex 3x3 Zagoruiko that incorporates three thematic defences, but the variations follow a clear logic.  Two tries and the key are made by the b7-rook, whose opening of the bishop line sets up a threat, 2.Qxd5.

Each of the three defences, 1…Bd4, 1…Raxa8, and 1…Rhxa8, leads to three changed mates.  But curiously some of these mating moves recur against different black defences, so that instead of a total of nine different mates, only six mates transpire – this idea is called a reduced Zagoruiko.

The first try 1.Rb4? supports the queen’s guard on d4: 1…Bd4 2.Qxd4, 1…Raxa8 2.Nd3, and 1…Rhxa8 2.Qh5, but 1…d4! refutes.

The second try 1.Rh7? shuts off the rook on h8: 1…Bd4 2.Qh5, 1…Raxa8 2.g4, and 1…Rhxa8 2.Rh5, but 1…Rd3! refutes.

Have a go at solving 78 which has, in addition to set play, a try phase that is attractively analogous to the actual play.

The solution will appear next month.

78. Michel Caillaud
British Chess Problem Society, Kingston 1999
Prize

Mate in 2

72. Miodrag Mladenovic
Mat Theme Tourney 1984
2nd Prize

Mate in 2

Solution to Problem 72 in the previous column:

The try 1.Ra8? threatens 2.Qb8, 1…Qh6 2.f4, 1…Ne4 2.Nf3, and 1…d4 2.Ra5, but 1…bxc3!

The key 1.Rf3! threatens 2.Qf6 and produces three changes, 1…Qh6 2.Qf4, 1…Ne4 2.Nf7, and 1…d4 2.Rc5.