Could you post what type of tactic is used?
Very hard puzzle from one of my games
After Qa5 Ra6, black plays Qxd2 and has a perpetual or more. However, I don't know what black does after Qa5 Nf1. Hmmm...maybe Qb4? Qa5 looks quite good! But what about Nb1?
After Nf1 or b1, I was thinking Qe1 and promote my own pawn. Material should equal out at the end for all the branches I calculated.
I agree with your calculations, falcongrine. If white should promote, Rxa8 and white plays Qxa8 and gets a check and black plays Kh7, but now the black queen is protecting e4 so white cannot do much better. If white takes the black bishop (Qxa3) then black promotes and has 2 queens on the 1st row
I looked it up with an engine, and although Qa5 is the best move for black, the position is winning for white. The correct response for white is Rc2, but the position may be drawn if white promotes.
@Maximus I don't know which engine you used, but the position is drawn after Rc2 as well (I let Houdini 3 run till depth 26). You have to find only moves then but it's still a draw. Also, I can't tell you the "type" used, because this is not a two-mover with a double attack and there are too many lines with different ideas.
P.S. Sorry for not answering so long, but in Germany it was 1 A.M. and I had to sleep.
Last year I played at the world youth chess championship in Maribor (Slovenia). In the 7th round I was always completely losing until I created some counterplay and had a chance to draw the game in this position:
I hope you enjoy the puzzle and I would be surprised if someone found the draw considering all major white tries in the first attempt.