Bilbo Discovers Smaug's Weak Spot
Bilbo Baggins's second descent into the Lonely Mountain's treasure-hall transforms him from a terrified burglar into a cunning intelligence-gatherer, and the single fact he extracts from Smaug—the location of a bare patch on the dragon's otherwise impenetrable armour—becomes the decisive piece of information that will ultimately bring about the dragon's destruction. The discovery is not a lucky accident but the product of a deliberate, risky verbal strategy, and it marks the moment when Bilbo's role shifts from passive observer to active agent in the quest's outcome.
The Riddle-Conversation and the Dragon's Vanity
When Bilbo creeps down the tunnel a second time, he finds Smaug only pretending to sleep; the dragon's left eye is half-open, watching the entrance. Smaug speaks first, taunting the invisible intruder: "Well, thief! I smell you and I feel your air. I hear your breath. Come along! Help yourself again, there is plenty and to spare!" Bilbo, remembering the danger of a dragon's spell, refuses to be drawn closer and instead engages Smaug in riddling talk, a tactic that plays on the dragon's fascination with puzzles and his immense vanity. Bilbo flatters Smaug with titles—"Smaug the Chiefest and Greatest of Calamities"—and the dragon, though suspicious, is pleased enough to continue the conversation. Bilbo describes himself in riddling epithets: "I am the clue-finder, the web-cutter, the stinging fly... I am Ringwinner and Luckwearer; and I am Barrel-rider." Smaug, deducing that the Lake-men are involved, grows boastful, declaring that his armour is "like tenfold shields, my teeth are swords, my claws spears, the shock of my tail a thunderbolt, my wings a hurricane, and my breath death!"
The Deliberate Probe and the Revealed Weakness
Bilbo, feigning a frightened squeak, challenges the dragon's claim of invulnerability: "I have always understood that dragons were softer underneath, especially in the region of the—er—chest; but doubtless one so fortified has thought of that." Smaug, stung by the implication, snaps back that his information is "antiquated" and boasts that he is "armoured above and below with iron scales and hard gems. No blade can pierce me." Bilbo then flatters the dragon's "waistcoat of fine diamonds," and Smaug, absurdly pleased, rolls over to display his gem-encrusted belly. "Look!" he says. "What do you say to that?" Bilbo exclaims aloud, "Dazzlingly marvellous! Perfect! Flawless! Staggering!" but his inner thought is a precise observation: "Old fool! Why, there is a large patch in the hollow of his left breast as bare as a snail out of its shell!" This is the crucial discovery—the one spot where Smaug's armour of scales and gems does not cover him.
Consequences and the Thrush's Message
Having secured the information he needed, Bilbo attempts to withdraw, but his parting shot—"And so do burglars"—enrages the dragon, who spouts terrific flames after him up the tunnel. Bilbo escapes with singed hair and a scorched back, but he carries the knowledge of the bare patch. Back on the doorstep, he tells the dwarves what he has learned, and the conversation turns to dragon-slayings and the possibility of exploiting the weakness. An old thrush, which Thorin identifies as a bird of an ancient breed that used to live about the Mountain, listens intently to all that is said. Bilbo, in his ill temper, throws a stone at the thrush, but Thorin rebukes him, explaining that the Men of Dale once understood the language of thrushes and used them as messengers. The thrush, having heard the secret of the bare patch, silently spreads its wings and flies away. It will carry the news to Bard the Bowman, who, guided by the thrush's message, will aim his last black arrow at the exact hollow in Smaug's left breast and slay the dragon as he swoops over Lake-town.
