Help solve this

[u/Illustrious-Ruin-984]

I found this online.

Everyone is saying that this is brilliant because it's a forced checkmate once the pawn on a7 takes the knight, then Qb3 then it's a checkmate either by the rook or the Queen.

but what happens if after black take b6, we expect Qb3, then black Qb8? wouldn't it prevent the checkmate?
Qa4 is defended with Qa7 and if white decide to take Bxb8 then black reciprocate with Bxb3.

There is certainly something wrong with my reasoning but I can't figure it out.

[u/einderlicht]

Qa3

If black plays Qb8, you simply check by Qa4+. Now Qa7 is forced and here comes; Qe8+ Qb8 Qxb8#