Originally posted by WulebgrNxa8
That's the given solution, but what if black does not grab the knight? For example, 1.Nb6 Bc5.
edit: drat, too slowagain...
edit 3: after Nxa8, 0-0 (what else?) white can play Rd8 to keep hold of the knight.
edit 4: although Be7 from black (rather than Bc5) cuts that out.