notyetagm: Position after 31 ...  c7-f4??:
click for larger viewBlack chose not to meet the threat to his undefended a4-knight by <COUNTERATTACKING> (i.e., making an equal threat) against the loose White d4-bishop. But unfortunately Black has forgotten that <Loose Pieces Drop Off> (<LPDO>). After the intended sequence 32 x a4  x d4, Black has a loose rook on d4 that is defended only by other pieces and an exposed king on c8. White continues 33 c6+  b8 34 xb6+, with a <DOUBEL ATTACK WITH CHECK> against the loose Black d4-rook, winning material. (VAR) Position after 31 ... xd4 32 c6+ b8 33 xb6+:
click for larger viewAs John Nunn wrote, <"If your king is exposed to check, you need only one undefended (loose) piece to lose material to a double attack">. A loose piece smack in the middle of the board (Black d4-rook), defended only by other pieces (i.e., not defended by a pawn), and an exposed king are just too many tactical liabilities for Black's position to withstand and he must lose material. | 
