1. William Whyatt Chess World 1957 

Mate in 2 
An incomplete block where 1…Kb2 2.Qxa2 is set, but no mate is available against 1…b3 initially. The key 1.Qe6! (waiting) yields a flight, 1…Kd3 2.000, provides for 1…b3 with 2.Qe2, and leaves 1…Kb2 2.Qxa2 unchanged.
2. Alexander Goldstein Lazard Memorial Tourney 1950 5th Hon. Mention 

Mate in 2 
Every possible black move has been provided with a set mate: 1…Sxf3 2.Sxf3, 1…Sxf4+ 2.Qxf4, and 1…Sgelse 2.Qe1. The waiting key, 1.Qh2!, keeps the 1…Sxf3 2.Sxf3 and 1…Sxf4+ 2.Qxf4 variations, but generates two new mates with 1…Se3 2.Rd3 and 1…Se1 2.Sc4, so this is a mutate.
3. Frederick Hawes & Frank Ravenscroft Chess Life 1956 

Mate in 2 
The key 1.Kc8! is a sort of anticipatory selfpin of the d7rook. The threat of 2.Rc7 is disabled by any black rook move, which pins the white piece by discovery. A random black rook move, 1…R~, allows 2.Qd4. Two correction moves by the rook prevent 2.Qd4 but they err by interfering with another black piece, 1…Rf4!? 2.Qc7, 1…Re4!? 2.Qxd5. The b2knight also produces correction play: 1…Sa4 is the ‘random’ defence that permits 2.Qe2; 1…Sd3!? corrects by eliminating the queen mate but selfblocks, 2.Bb3. Also, 1…Bxe5 2.Sxe5, 1…d4 2.Qc5.
4. John James O’Keefe Brisbane Courier 192021 2nd Hon. Mention 

Mate in 2 
After a waiting key, 1.Qa4!, the white queen has two potential mates on d7 and d1. Both are currently stopped by the black queen, which is focusing on the defensive squares d6 and d2. If Black moves the queen, the focus cannot be maintained and White exploits this accordingly, 1…Qg5 (or to f4, e3, etc.) 2.Qxd7, and 1…Qg6 (or to f6, e6, etc.) 2.Qd1. Some pawn defences lead to the same queen mates due to selfinterference, 1…g6 2.Qxd7, 1…g5 or 1…e3 2.Qd1. A good variety of traditional play occurs in the remaining variations, 1…e6 2.Rd6, 1…d6 2.Sb6, 1…c3 2.Qxe4, 1…Rany 2.Sxe7, 1…Sany 2.Qxc4.
5. Andy Sag OzProblems.com 2010 

Mate in 2 
The key 1.Rxg3! threatens 2.Rxh3 and allows a check. The threat and ensuing seven variations generate mates from each of the eight ranks. 1…Rxg3+ 2.hxg3, 1…Rxh2 2.Rxh2, 1…Rh4 2.Qxh4, 1…Kh5 2.Qg5, 1…Sf3 2.Qxg6, 1…Rh5 2.Qg7, 1…Bxe6 2.Qh8.
6. Arthur Willmott British Chess Magazine 1983 

Mate in 2 
A nice key 1.Qb2! gives a flight on c6 and threatens 2.Se7. When the black king takes the flight, White mates with a switchback: 1…Kxc6 2.Qb7. The wellutilised white queen delivers three more mates, 1…Sxc6 2.Qa2, 1…Sc8 2.Qb5, 1…e3 2.Qg2. Also, 1…Rxe6 2.Rc5.
7. Thomas Denton Clarke The Australasian 1876 1st Prize 

Mate in 2 
The unprovided flight 1…Ke4 signals the solution somewhat – 1.Qe1! (waiting), which answers 1…Ke4 with the pinmate 2.Qh1. The key is still good though, in that the queen abandons the Q + S battery while preparing to support the white pawn in the star variation, 1…Bany 2.e4. Two more lines are unchanged from the set play, 1…Sany 2.Bxc4, and 1…e4 2.Rg5.
8. Geoff Foster The Problemist 2001 3rd Prize 

Mate in 2 
Two tries and the key trigger three connected phases of play, and bring about a remarkable combination of themes. The first try 1.Bxd2? threatens 2.Rh4, and when Black defends with the rook or the knight, White is able to mate with the b5knight, because c3 is guarded: 1…Rh1/Rg1 2.Sa3, 1…Sd6/Se5/Sg5/Sh6 2.S5d6. But 1…e1(Q)! defeats the try. The second try 1.Be3?, with the same threat of 2.Rh4, observes c5 so that the b7knight can mate instead after the same black defences: 1…Rh1/Rg1 2.Sa5, 1…Sd6/Se5/Sg5/Sh6 2.S7d6. Now 1…d1(Q)! refutes the try.
9. Peter Wong Chess in Australia 1988 

Mate in 2 
The white queen makes five tries and the key that can be grouped into pairs of moves to the same file, and where the second move of each pair “corrects” the first by providing for 1…Rxa8 or 1…Rxh8. 1.Qa4? (waiting) Rxh8! and 1.Qa1? (waiting) Rxh8 2.Qxh8, but 1…e5! 1.Qe5? (threats: 2.Qxe7, 2.dxe7, 2.dxc7) Rxa8! and 1.Qe4? (2.Qxe7, 2.dxe7) Rxa8 2.Qxa8, but 1…cxd6! 1.Qc5? (2.Qxc7, 2.dxc7, 2.dxe7) Rxh8! and 1.Qc3! (2.Qxc7, 2.dxc7) Rxh8 2.Qxh8, 1…exd6 2.Qf6, 1…c5/c6 2.Qa5 (1…cxd6 2.Qa5/Qxc8/Rxc8), 1…Rg8 2.Rxg8, 1…Rf8 2.Rxf8.
10. Ian Shanahan Problem Observer 1995 1st Hon. Mention Ded. to John F. Ling 

Mate in 2 
The key 1.Qxb7! unpins the black pawn on d7 and simultaneously selfpins the white queen on the long diagonal. The threat of 2.Qe4 is countered by 1…d5, but now the pawn has unpinned the queen – returning the favour – and so allows 2.Qf7. Such a sequence of (1) unpin of Black by White, (2) selfpin of White, (3) unpin of White by Black, and (4) mate by White, all executed by one pair of pieces, is called the Schór theme. Another unpin of the queen occurs with 1…Sc6 2.Qxd7. In a supplementary pair of variations, the black bishop on f3 also gets unpinned twice, as the defensive motive, 1…Bf4 2.Sg7 and 1…Sf4 2.Sg3. There is byplay, 1…Rd5 2.Qxd5, 1…Re5 2.Sd6.
11. Rurik Bergmann & Brian Tomson Chess in Australia 1983 

Mate in 2 
The tries 1.Rb7? and 1.Rb8?, threatening a rook mate on the dfile, fail to 1…d2!, which creates a flight on e3. A good sacrificial key 1.Bb2! (waiting) pins the c3pawn and so provides for 1…d2/dxc2 with 2.Qd2, and if 1…cxb2 2.c3. The g4rook is guarding against queen mates on f4 and g1, and when the piece moves its focus on the two squares is lost: 1…Rgfile/Rf4 2.Qf4, 1…Rh4/Rg1+ 2.Qg1; only 1…Re4 prevents both mates but it selfblocks, allowing 2.Sf3. 1…Rarandom 2.Rb4, 1…Rc4 2.Sb3.
12. Denis Saunders The Problemist 1983 2nd Commendation 

Mate in 2 
Set mates are provided for most of Black’s moves, other than a random bishop move like 1…Bc1. A very fine key 1.Sd5! (waiting) adds two variations by sacrificing the knight to a couple of black pieces, 1…exd5 2.Qf5 and 1…Kxd5 2.Se3. The latter is an indirect battery mate that also takes advantage of the pinned black bishop. Another pinmate occurs after 1…Kd3 2.Qf3. A random bishop move, 1…B~ allows 2.Sxc3, while 1…Be1 gives 2.Rfxe1. Also, 1…Sany 2.Qd4, 1…e5 2.Qf3.
13. Henry Charlick Bignold’s Chess Annual 1895 “The Siamese Twins” 

Mate in 2 Twin (b) Remove Pb3 
In part (a), the key is similar to that of the previous problem, a double sacrifice to Black’s king and pawn – 1.Ra2! (waiting). 1…Kxa2 2.Sc3, 1…Kxc2 2.Sa3, 1…bxa2 2.Sa3, 1…bxc2 2.Sc3. In (b), White sets up an indirect battery on the bfile with 1.Rb8! (waiting). 1…Ka2 2.Sc3, 1…Kxc2 2.Sa3. No changed play between the two parts (perhaps that’s why the problem is called “The Siamese Twins”!?), but this is a neat miniature presenting five model mates; only 1…Ka2 2.Sc3 in (b) isn’t a model because the b2bishop is doubly guarded.
14. Arthur Mosely Good Companions 1916 

Mate in 2 
Set mates are available against all of Black’s moves: 1…Sfany 2.Se3 (1…Sd4 2.Se3 or 2.c4), 1…Sgany 2.Re5, 1…c4 2.Ra5. After the key, 1.Re2! (waiting), a new mate follows 1…Sfrandom – 2.Rd2, and the correction 1…Sd4 allows 2.c4 only, removing the dual of the set play. 1…e6/e5 2.Sf6 is an added variation, and the remaining play is unchanged, 1…Sgany 2.Re5, and 1…c4 2.Ra5. A classy mutate!
15. Laimons Mangalis American Chess Bulletin 1956 1st Hon. Mention 

Mate in 2 
The Novotny try 1.Se6? (threat: 2.Rc5) shuts off the e7rook and g8bishop, so that they no longer guard the potential mating squares e5 and d5. When Black defends with the d3rook and c3bishop, they cause a Grimshaw interference that permits White to mate on those squares: 1…Rd4 2.Se5 and 1…Bd4 2.Bd5 (1…Rdelse on file 2.Rxc3). But 1…Rxe3! refutes the try. The key 1.Bd4! (threat: 2.Qa6) is another Novotny but it cuts off the d3rook and c3bishop instead, and now it’s the e7rook and g8bishop pair that effects a Grimshaw: 1…Re6 2.Bd5 and 1…Be6 2.Se5. The two white mating moves are thus transferred from one pair of black defences to another. Excellent, sophisticated strategy, but it’s a pity that there is no byplay at all.
16. Andy Sag OzProblems.com 26 Feb. 2011 

Mate in 2 
The sacrificial key 1.Qb8! (waiting) is also an ambush move, preparing to strike at e5 when the black bishop moves off the queen’s line, 1…Bxa3, etc. 2.Qxe5. 1…Bxb8/Bc7 opens the white bishop’s line to the flight on e7 and enables 2.e8(S). The other white pawn also underpromotes, when Black takes the flight, 1…Kxe7 2.g8(S), and if 1…Kxg7 2.Qh8.
17. Ian Shanahan Problem Observer 1994 1st Commendation In memory of A. R. Gooderson 

Mate in 2 
The white queen unpins the black knight with the key 1.Qd7!; the threat of 2.Qf5 is stopped by any move of the unpinned knight, which pins the keypiece by discovery. Such an unpinpin sequence is called the Dalton theme. A random knight move, 1…S~, allows 2.Qxd3. Three correction moves by the knight disable this secondary threat but permit new mates: 1…Sb4 2.Sc5, 1…Sf4 2.Sg5, and 1…Se3 2.f3. There are two byplay variations, 1…Rxb3/Rf3 2.Qxd5 and 1…e6 2.Qh7.
18. Frank Ravenscroft Problem 1963 

Mate in 2 
The key 1.Sxd3! (threat: 2.S7c5) grants a flight on e4 and forms a second battery on the dfile. 1…fxe4 selfblocks and allows 2.Sf4, and 1…f4 interferes with the black queen and leads to a switchback mate 2.S3c5. The R + S battery fires in the variations 1…Qxf6 2.Sxf6 and 1…Kxe4 2.S7c5; the latter is distinct from the threat considering that 2.S7c5 has become an indirect battery mate, with the king on e4. Also, 1…cxd3 2.Qa4. A splendid battery play problem.
19. H. P. Williams The Sydney Morning Herald 1895 1st Prize 

Mate in 2 
Not 1.Rg1? (threat: 2.Qxh5) because of 1…Kh4! The surprising waiting key 1.Rg2! gives two flights to the black king: 1…Kh4 2.Rxh2 (a pinmate), 1…Kxg2 2.Qf1. The active white queen delivers three more mates with 1…Rxg2 2.Qxh5, 1…Rh1 2.Qxh1, and 1…Shany 2.Qg4. Two further variations are unchanged from the set play: 1…Rh4 2.Rg3, and 1…Sgany 2.Rg3. This gem of a waiter deserves to be remembered from more than a century ago!
20. William Whyatt Sunday Telegraph 1961 

Mate in 2 
The diagram is a complete block where every black move has a set reply, 1…Bb7 2.Qxb7, 1…Bc6 2.Qc4, 1…R~ 2.Qd7, 1…Rd6 2.c6, 1…Bf~ 2.Se7, 1…Bxd4 2.c4, 1…g4 2.Sf4. Any white king move could solve by maintaining the block, but in three cases Black is able to refute with a subtle, pinning defence: 1.Ka4? Bc6!, 1.Kb4? Rb8!, and 1.Kb2? Bxd4! Only 1.Ka2! works, avoiding the pins. A classic rendition of the idea, this twomover is perfectly constructed, with not a plug in sight.
21. Arthur Willmott The Problemist 1998 

Mate in 2 
The thematic defences are 1…Sf4 and 1…Sf2, both unpinning the white queen. As initially set, 1…Sf4 permits 2.Qe4, and 1…Sf2 leads to 2.Qh5. After the key, 1.Be4! (threat: 2.Sd3), the unpins are exploited in a different way: 1…Sf4 2.Qc3, and 1…Sf2 2.Qg3. So two orthogonal mates in the set play are changed to two diagonal ones in the actual play. The byplay consists of a pinmate, 1…exd5 2.Qf5, and 1…Sc5 2.Qxf6.
22. John James O’Keefe Brisbane Courier 1916 2nd Prize 

Mate in 2 
All initial black moves have been provided with set mates, 1…Sg~ 2.Bf3, 1…Se4 2.Se3, 1…e4 2.Se3, 1…exd4 2.Bf3 or 2.Bxe6, 1…c4 2.Qxd7, 1…cxd4 2.Qc6, and 1…Sd~ 2.Rxe5. Unusually, such a block position is here solved by a key that contains a threat: 1.Rd2! (threat: 2.dxe5), making this problem an example of a blockthreat. 1…Sf3+ 2.Bxf3, 1…Se4 2.Se3, 1…e4 2.Se3, 1…exd4 2.Bf3 (removing the dual of the set play), 1…c4 2.Qc6 (changed mate), 1…cxd4 2.Qc6, and 1…Ke4 2.dxc5 (added mate). Fine flightgiving key and halfpin play.
23. Geoff Foster The Problemist 2008 (Version of The Problemist 2003, 2nd Prize) 

Mate in 2 
Four tries and the key (all waiting moves) deal with the three thematic pawn defences, 1…dxc4, 1…dxe3, and 1…c2, in a wonderful variety of ways. 1.Qxc6? 1…dxc4 2.Qxe4, 1…dxe3 2.Qxd5, but 1…c2! 1.Qh3? 1…dxe3 2.Qxe3, 1…c2 2.Rd2, but 1…dxc4! 1.Kf4? 1…dxc4 2.Qxd4, 1…c2 2.Rd2, but 1…dxe3! Hence each pawn defence also acts as the refutation against a different try, providing a nice balance. An additional try is 1.cxd5? 1…dxe3 2.dxc6, 1…cxd5 2.Qb5, but 1…c2! After the flightgiving key 1.Ra2!, two of the three pawn defences provoke brand new mates, 1…dxc4 2.Qxd4, 1…dxe3 2.Be2, and 1…c2 2.Ra3. If Black takes the flight, 1…Kxe3, then 2.Qh3.
24. Anthony Vickers Chess in Australia 1975 1st Place 

Mate in 2 
A good key 1.Sxg5! (threat: 2.Qf4) selfpins two white pieces – the knight on the gfile and the rook on the long diagonal, and allows them to be captured with check. These pieces are unpinned in the variations 1…Sd5 2.Rf5 and 1…Qf7 2.Sxf7, while their captures lead to 1…Bxf3+ 2.Sxf3 and 1…Qxg5+ 2.Qxg5. The black queen forces two more mates, 1…Qxf8 2.Re6 and 1…Qc4 2.Bg7. Lastly, 1…Sd3 2.Sxd3 and 1…Bc1 2.Qd4.
25. Brian Tomson Problem Observer 1980 4th Prize 

Mate in 2 
The thematic key 1.Bb8! (threat: 2.Rc8) opens the 7th rank and enables the black pawn and rook pair to check by discovery. Three crosscheck variations ensue, when White answers the checks by interposition and delivers mate simultaneously: 1…exd6+ 2.Rc7, 1…e6+ 2.Sd7, and 1…e5+ 2.Se7; in each case White takes advantage of the pawn’s selfblock. The byplay consists of 1…Qxd6 2.Rxd6, 1…Sd4 2.c4, and 1…Se5 2.Sxe7.