Use when assessing your own or a team's actual position — strip the self-flattery first, THEN plan. Use when someone's strategy is sophisticated about the enemy but naive about themselves.

This looks like a contradiction but is actually an extension on a different axis. Sun Tzu's deception is outward (mislead the enemy). Musashi's honesty is inward (don't flatter yourself, don't rationalize). A strategist who deceives the enemy brilliantly but lies to himself about his own strength is the exact failure both books, together, name.