Advance the c‑pawn to c9 as a screen, then the cannon captures the defending knight on e9, delivering a decisive check and forcing the king into a losing position.
The black knight on e9 is the linchpin protecting the king e10, supported by the two advisors at d10 and f10. Red has only a cannon on b9 and two pawns, but by pushing the pawn from c8 to c9 Red creates a screen for the cannon. The cannon’s capture b9‑xe9 checks the king; the king cannot capture because the pawn on c9 now attacks d10, removing the last shield. If the king does take the cannon, the pawn on c9 gives a discovered check on d10, and the remaining material (the a‑pawn advancing) seals the mate. The lesson is the classic pawn‑screen technique to unleash a powerful cannon attack, turning a minimal material advantage into a forced win.