A Narrow Escape

In my last session with Pyre, one of the positions we discussed was the following:

Kobaidse - Zereteli, Tbilissi 1970. Black to move

Black has a serious problem: the knight on b6 is in deep trouble and might very well fall to White's mobile Bishops. White's plan seems obvious: after the black Knight retreats to a8 (an abysmal square for a Knight), White can win the piece if he manages to bring his light-colored Bishop to b7.

However, White's most direct approach to win the Na8 fails: after
1. ...     Na8 
2. Bc8 threatening Bb7 to win the Knight. However, Black can now play
2. ...     Ke8! this forces White's Bd8 off the a5-d8 diagonal, after which Black's Knight can escape safely via c7. The game should quickly end in a draw.

However, after 1. ... Na8, White has a much stronger move than Bc8. If White plays 2. Bh5+!, Black's position is hopeless:

Analysis Diagram after 1. ... Na8 2. Bh5+!

Black's Knight on a8 can't move, and the King is cut off from the e-file. White is simply going to march his King to e6, grab the d-pawn, and win the game without difficulties.

So it is clear that Black's most obvious attempt to save the position by playing Na8 does not work. Therefore, he came up with a much more radical solution, a solution that I didn't find when I analyzed the position. Black played

1. ...         Ke8!! Black simply leaves the Knight en prise
2. Bxb6    Ke7!!

This results in the following position:

This position is - remarkably - drawn

White is now a whole bishop up, but can't capitalize on it because Black has cleverly encaged the Bishop on b6. It can not escape, and sacrificing it for one of Black's pawns also doesn't help because the resulting opposite-colored bishops endgame is dead drawn.
In the diagram position, Black simply moves his Bishop back and forth between b4 and e1, and there's no way how White can improve his position. A remarkable position indeed.

I found this example not just interesting in itself, but I was also intrigued by the fact that I did not find the solution on my own. Admittedly I didn't spend too much time on this, but typically when I fail to solve a chess puzzle, it's because I can not solve all the calculations involved. In other words, I fail tactically. In this case I failed strategically because I didn't see the idea of trapping White's Bishop. In other words I failed strategically.