What is the most important thing Bilbo learns from Smaug? He learns where Smaug’s weak spot is – he has an unprotected spot on his left breast.

What did Bilbo learn during his conversation with Smaug?

During the conversation, however, he looks for the vulnerable spot on Smaug’s body. Bilbo knows Smaug must be killed and, rather than avoiding it, Bilbo develops a strategy for accomplishing it.

What weakness does Bilbo discover in Smaug?

Bilbo finally gets fed up and tells Smaug his crew is there for revenge, that there’s about to be a new king under the mountain. Smaug laughs at him, because he’s basically invincible and there’s nobody left to challenge him (that he knows about). Bilbo mentions a dragon’s typical weak point — its belly.