Calculation exercise 2

This position is very famous. It’s from the brilliancy prize-winning game Averbach-Kotov, Zurich 1953 (as featured in everyone’s favorite tournament book, by David Bronstein).

The challenge is to calculate the specific consequences of 30…Qxh3+. Does it lead to a forced mate or not?

In my opinion this is a little different from the last exercise I posted; this is a bit more of a straight-line calculation, i.e. it offers fewer candidate moves and fewer reasonable branches in the analysis tree. That should make it possible to calculate further.

To review, Kotov’s improvement method was to set aside a significant amount of time, analyze over a real board without moving the pieces, and then write out the tree of variations you’ve calculated. Then compare versus GM (or Fritz) analysis.