Originally posted by kbaumenwell, depending on where the rook goes, it is either
Yep, Qb2 was also what I found, black has to move a rook followed by 2.c4# or 2.g4#.
- Ra4 2.c4#
- Rb4, 2.cxb4#
- Rd4 2.cxd4#
- Rcxe4 2.c4#
- Rxc5 2.c4#
- Rxc3 2.Qxc3#
- Rh4 2.gxh4#
- Rf4 2.gxf4#
- Rgxe4 2.g4#
- Rxg3 2.Bxg3#
- Rxg5 2.g4#