Smaug the Golden was the dragon that drove the dwarves out of their halls in the Lonely Mountain.
Later, Balin, Dwalin, Kili, Fili, Dori, Nori, Ori,
Oin, Gloin, Bifur, Bofur, Bombur and their leader
Thorin Oakenshield, together with Bilbo Baggins from Bag End ang Gandalf the Grey travelled to the Lonely Mountain to defeat Smaug and win the gold and the mountain back.
Smaug was killed by Bard with an arrow when he was attacking Esgaroth.