The story attached here is Luo Cheng secretly toppling the Bronze Banner, from the Sui and Tang hero novels. A Sui general built a battle formation around a great bronze flagpole at a mountain pass, and Qin Qiong could not break it. The young general Luo Cheng was ordered to guard the banner, but Qin Qiong was his cousin, and his mother told him privately to help. On the day of the battle Luo Cheng appeared to defend the formation, then turned, brought the banner down, and joined his cousin's side. Editions say the story teaches judging by reason rather than outward loyalty. The link to this middle stick is loose: a pledge made quietly and kept matters more than what is said in public, much as the poem's unpaid vow still binds.