In 2941, Thorin, Thrain’s son, met with the wizard Gandalf, who tried to convince him to regain possession of Erebor. Thorin and his kinsmen and companions, with the help of Bilbo Baggins, set out on their journey. Thorin was able to enter the treasury through the underground passage through which his father and grandfather had escaped. Realizing that the forces were unequal and it was useless to fight, Thorin was going to steal some of the treasures (including the Arkenstone).
However, the dragon noticed him, and the army was attacked on the slopes of the Mount of Erebor. The squad miraculously managed to survive. The dwarves fled into the mountain, and the enraged Smaug unleashed his fury on the people of Esgaroth, who had provided help for Thorin and his squad. However, Smaug was killed by Bard the Bowman. The Dwarves, led by Thrain’s son, managed to get Erebor.