2024/03/29 DPA: "BQM [Backward Queen Move] OMG!"

White to move.

Black's King has no escape squares but how does White deliver check without disturbing the mating net?

1. Rf1+ Qf2  2. Rxf2+ Rxf2 and White has won the heavy exchange but he started out down a Bishop so he has won a Queen for a Rook and Bishop.

This probably isn't the solution since it was trivial to spot.

If the Black Rook wasn't guarding the d file, White could continue 3. Qd4+, forking the King and Rook.

Whatever White does, he must not move the g pawn due to ... Qh2#.

Is there any Intermezzo White can play after 1. Rf1+ Qf2?  Doesn't appear so. 

White doesn't have time for 2. d4 to prep for 3. Qe5+ and anyway, this allows Black to escape to g6.

White lacks control of the dark squares:  every dark square the Queen could move to is already controlled by Black.

1. Qf3+ allows 1. ... Qf4, which not only blocks check and attacks the White Queen, it also attacks the Rook on c7.  This line doesn't look good.

If the White Queen moves off the a8-h1 diagonal, Black gets ... Qxg2#.

Is there any value to luring the d Rook off of the d file or even off of the back rank?  It doesn't appear so.

1. Rf1+ could also be met with 1. ... Qf4, which is a more active square for the Queen.

And by playing 1. Rf1+, White allows the Black Queen to attack the Rook, thus forcing the issue:  does White want this?  Maybe not.

No, 1. ... Qf4 is terrible due to 2. Rxf4+ gxf4  3. Qxf4 Kg6  4. Qxf7+, winning the Bishop.

BQM [Backward Queen Move]?  No.

LQM [Lateral Queen Move]?  Nope:  any such move takes the Queen away from the defense of g2.

Queen sac?  No.

Zugzwang?  Hardly.

1. Rf1+ Qf2  2. Rxf2+ Rxf2  3. Qe1, attacking the Rook.  If 3. ... Rb2  4. Qc3+, winning the Rook.  No, it doesn't:  4. ... Kg6 uncovers the Bishop X-Ray defense of the Rook.

And besides, Black could have played 3. ... Rf4/5.

If the White Queen can somehow hit f7 without losing tempo, he has an attack.  Can the c Rook somehow play a role in enabling this idea?

1. Rf1+ Qf2  2. Rxf2+ Rxf2  3. Qb7 [trying to hit f7] Kg6 [discovering the Rook defense of f7].

3. Qb4 [trying to get to e7] Bf8.

I've exhausted the possibilities.  Let's look again from the starting point.

Qf3+ is good because it hits f7 along with the Rook.

But White can't play this initially due to 1. ... Qf4.  And White can't play 1. g3 to prevent ... Qf4 due to 1. ... Qh2#.

1. Qf3+ Qf4  2. Rf1 Qxf3  3. Rxf3+ but even if White wins the Bishop, this is only even material.

Playing a pre-emptive Rxf7 doesn't help.

1. h4 but Black can ignore that and play 1. ... Qf2, preventing Rf1+ and also opening up the h file if 2. hxg5+ hxg5 and ... Rh8+ is a threat.

White can push 2. h5, which cuts off the g6 escape so now the Queen can move off of that diagonal.

But that gives time for 2. ... Qd4 and if 3. Qf3+ Qf4.

1. Qf3+ Qf4  2. Qb7 is not possible due to Black's b Rook.

1. Qf3+ Qf4  2. Qh5, hitting f7.  But 2. ... Rf8 defends.

1. h4 Qf2  2. h5 Qd4  3. Rf1+ Qf2  4. Rxf2+ Rxf2  5. d4 but Black can defend with 5. ... Rd5 or Rf5.

Still, I'm thinking of options.

I see something promising:  1. Rf1+ Qf2  2. Qe1.

What does this accomplish?  It doubly attacks the Queen.  Since the Black Queen is pinned, it cannot capture the White Queen and Black cannot add another defender.  So the Black Queen must capture the Rook. 

How is this different from 2. Rxf2+?  The White Queen now controls the f file.

2. ... Qxf1  3. Qxf1+

• If 3. ... Ke5  4. d4+ Kxd4  5. Qd1+ skewering the King
  • 4. ... Kd5  5. Qf3+ Kxd4  6. Qd1+
    • 5. ... Kd6  6. Qc6#
  • 4. ... Kd6  5. Qc4, threatening 6. Qc5#
    • If 5. ... Bxd4  6. Qxd4+ Kxc7  7. Qxb2

A bit involved but this is the best I can find.  Let's try it.

I was right although the puzzle stopped at 3. Qxf1+ probably precisely because of how involved the subsequent line was.

If the only goal was to win the heavy exchange, then 2. Rxf2+ would have been adequate.  Obviously, there's something more to it than that.

No, I overlooked 3. ... Rxd4.  So my idea of 3. d4+ was flawed but the point of the puzzle was to take over the f file and hit f7, which I did recognize but somewhat later in my analysis.

The key was recognizing that 2. Qe1 doubly attacked the Black Queen [yellow] but the Black Queen could not capture the White Queen [red] due to the pin [blue].  So the Black Queen had to capture the Rook which allowed White to win the heavy exchange AND control the f file, which will lead to a significant advantage.