1.
[{B:1q5k/4R3/8/8/1p6/1B6/5R2/1K6}
{V:White to play and mate in three. Try your solution on the board.;f2a2;
Correct;Incorrect.;The e7-rook and b3-bishop box Black's king into the corner, so if only White could check with his other rook, it would be mate. But the obvious moves by the f2-rook don't work, because Black's queen is able to cover both the potential mating squares, for example after 1 Rf6? Qf4! or 1 Rg2? Qg3! Black can exploit a stalemate defense. So how about trying a non-obvious move?}]

2.
[{B:1q5k/4R3/8/8/1p6/1B6/5R2/1K6}
{S:f2a2}
White only needs to give a check with his f2-rook and Black will be mated. But how is the rook to avoid the unwelcome attentions of Black's queen? All the obvious moves allow the queen to cover both mating squares, the one on the h-file and the one on the eighth rank. After 1 Rf1? Qa8, 1 Rf7? Qg8 or 1 Rf3? Qc8 White hasn't achieved anything, 1 Rf5? Qe8! may win the queen but it doesn't mate in three, while in the lines 1 Rg2? Qg3! and 1 Rc2? Qc7! Black uses a stalemate defense to stay White's hand. If White plays Bc4, Black replies with 1...Qb3. Perhaps the most unlikely-looking square for the rook, but there is a kind of logic behind it. The other rook moves failed because Black's queen could always move so as to cover the two potential mating squares. Playing the rook to a2 succeeds because Black's queen is already covering the mating squares at a8 and h2. If Black could pass he would be safe, but he has to move his queen, which is obliged to abandon control of either a8 or h2, for example 1...Qg3 2 Ra8+ or 1...Qg8 2 Rh2+.]
