1. Ke3 Bg2

1... Bh1 2. Qe7+ Kg8 3. Qe8+ Kg7 4. Qg6+ Kf8 5. Qh6+.

1... Bb1 2. Qd5.

2. Qa7+ Kf8

2... Kg8?? 3. Qa2+.

2... Kh8 3. Qf7 Bc6 4. Qf8+ Kh7 5. Qc5 Bg2 6. Kf2 Be4 7. Qc4.

3. Kf2 Be4

3... Bh1 4. Kg1 Be4 leads to the same thing.

4. Qe3 Bh1 5. Kg1 Bb7 6. Qc5+ Kg8 7. Qb5

and wins.

Reference(s): Storming the Fortress, IRLchess, November 14, 2018.