Mate in 2

The B+P battery along a1–e5 naturally draws attention. To set it off, the bishop on c4 must give way. This points to the tempting try 1.Bd3?, carrying the threat of 2.Re4#. Black can defend only by moving the knight on d5, allowing the queen on c6 to control e4; however, a random move of the bN, such as 1...Nb6, runs into the battery-mate 2.c4#. The true refutation is 1...Nf6!, which not only guards e4 but also opens a flight (e6) for the bK, cutting off White’s rook on h6. Therefore, the bishop on c4 must stay put, maintaining its x-ray grip on e6.

Having seen why 1.Bd3 fails, we consider a second try: 1.Nh4?, threatening 2.Nf3#. Once again, Black can defend only by moving the knight on d5, allowing the queen on c6 to cover f3. Almost every knight move now is met with a precise answer: 1...Nc7 2.Nxc6#; 1...Nf6 2.Neg6# or 2.Nhg6#; 1...Nb6, 1...Nxe7, or 1...Ne3 2.Re6#; 1...Nb4+ 2.cxb4#; and 1...Nxc3+ 2.Bxc3#. The exception is 1...Nf4!, which not only guards against the threat but also grants the bK an escape square (e4), cutting off White’s rook on g4 — just as in the first try, where the rook on h6 was cut off.

With the failures of 1.Bd3 and 1.Nh4 in mind, we finally arrive at the actual key: 1.Ng3!; threatening 2.Re4#, it forms a clever middle ground between the two tempting tries, blending their ideas while avoiding their pitfalls. What follows is a textbook demonstration of Black Correction:

Any random move of the bN allows Bc4 to assert control over e6 — what we may call the primary error — leading to 2.Re6#. The reply 1...Nc7 corrects this primary error by guarding e6, but in doing so it produces a secondary weakness: the queen on c6 is left unprotected, allowing 2.Nxc6#. Similarly, 1...Nf4 and 1...Nf6 are also correction moves, preventing Re6#, but both incur secondary self-block defects, resulting in 2.Rg5# and 2.Ng6#. Finally, the checks 1...Nb4+ and 1...Nxc3+, again acting as corrections, are countered by 2.cxb4# and 2.Bxc3#, respectively, with the a1-bishop coming into play to complete the picture.

A masterful problem, full of subtle points, by the trio of Indian composers!