10. Nxb5!
Rather than find a safe square for his bishop, Morphy finds a way to continue his attack and open lines to the Black king. If Black accepts the knight, White has a powerful attack.
10. ... cxb5?
This is the most logical move, but Qb4+ was better, as it forces the queens to come off the board. Of course, even without the queens, White would have a winning advantage; however, cxb5 is much worse for Black, as it exposes his king to attack.
11. Bxb5+
White claims a second pawn for his knight, while also forcing Black to respond to a check.
11. ... Nbd7
The most reasonable way to block White's check. Kd8 was also possible, but it's hard to justify moving your king into an area where so many pieces will be able to attack it.
12. 0-0-0
White castles to the queenside, bringing us to our next key position.
