
Solution

1… Rxd1 2. Rxd2 Rxe1 wins a piece in the process.
The point is that 1… Rxd1 captures the defender of the f2-square and threatens Rf2#
Ie. 1… Rxd1 2. Rxd1? Rf2#
1… Rxd1 2. Rxd2 Rxe1 wins a piece in the process.
The point is that 1… Rxd1 captures the defender of the f2-square and threatens Rf2#
Ie. 1… Rxd1 2. Rxd1? Rf2#