Puzzle of the week #66

Level: 
4-Rook
Chess Diagram: 

--------
-------K
--------
--------
------Q-
-----R--
------bP
------k-

In the first quarter of the 20th century a lot of chess lovers did some incredible work by composing some unforgettable puzzles. That was a time when the attack was all it mattered, there were no computers around to crush down to Earth spectacular sacrifice ideas, nor anyone was much interested to play defence. Gunnar Thoren is a name I haven't heard a lot, but this present puzzle he composed in 1927 has an interesting twist to it. Your tasks:
a) White to move and mate in three (10 points)
b) Which are the two objectives White must achieve in order to win? (10 points)
Total available points for this puzzle is 20. The answers will be published next week together with puzzle #67.

Puzzle #65 solution:
Considering the low number and not very good responses I got, we went over this puzzle during our Thursday night class. The complete solution has been discuss extensively and presented as a hand out. Those club members already in Victoria for the Grand Pacific Open or who could not make it to the club can request an electronic copy of it. There was only one student who got the right idea from the beginning: Andy Qian. Karl and Andy Yee were the other ones to get it on the second try. Congratulations to all 3 for their chess sense! While the winning idea and lines are not easy, analysing the position and listing those strategic and tactical concepts should have been the easier of the two. Unfortunately nobody mentioned more than 3 concepts, missing a good chance to score valuable points in the race... Here I am going to present just the bottom line solutions:
a) The best idea is to use the powerful passed "d6" pawn and do our best to stop "Rg3" from catching it.
1.Ra3!! ... This is an excellent decisive move. Whatever Black does, White will win.
I) 1... Rg8 2.Rh3+ Kg7 3.Rg3+ Kf7 4.Rxg7+ 1-0
II) 1... Rg7 2.Rh3+ Kg8 3.Rg3 Rxg3 4.d7! 1-0
III) 1... Rg6 2.d7 Rd6 3.Rxa7 Kg6 4.Ra6 Rxa6 5.d8Q 1-0
The main line is:
1... Rxa3 2.d7 Ra1+ 3.Kg2 Ra2 4.d8Q Rxc2+ 5.Kf3 Rc3+ 6.Ke4 Re3+ Now Black has managed to defend the important passed pawn "e5" and hopes to be able to push these 2 pawns with the help of the Rook.
7.Kf5! ... Unfortunately now White corners the Black King and threatens to mate it easily. The Black Rook will have to come to the rescue, but then he will lose his pawns. The endgame Queen against Rook is very much one sided.
b) Strategical and tactical concepts used:
Passed pawn
Promotion
Blocking
Square rule
Interference
Skewer Pin (relative/ absolute)
Discovered check

Correct solutions:
Andy Q - 24 points
Karl - 21 points
Joshua, John - 15 points
Andy Y - 12 points
Wilson, James - 11 point
Marcus - 2 points

STANDINGS

John - 288 points
Joshua - 286 points
Andy Qian - 278 points
Jeremy - 235 points
Karl - 233 points
Mark, Andy Yee - 223 points
James - 167 points
Wilson - 143 points
Humphrey - 111 points
Marcus - 101 points
Katerina - 87 points
Jacky - 80 points
Nathaniel - 52 points
Joanne - 21 points
Darren - 20 points

Comment: 

Material imbalance endgame