The Front Gate
The Front Gate is the great entrance to the Lonely Mountain, carved into the southern cliff-face where the Running River springs forth. It is a tall arch, once adorned with intricate carvings, now worn and blackened by the dragon's passage. The river issues from a dark opening in the rock, flowing through a narrow channel beside a stone-paved road wide enough for many men abreast. This was the main gate of the dwarves' kingdom, the way through which their wealth and traffic once passed, and the point through which Smaug first entered and later emerged to terrorize the surrounding lands.
The Dragon's Gateway
Smaug used the Front Gate as his primary exit and entrance. When he first came to the Mountain, he flew up from the North, settled on the peak in a spout of flame, then descended and crept in through the Front Gate, routing out all the halls and taking the treasure for himself. Later, he would crawl out of the great gate by night to attack Dale, carrying away people to eat. After Bilbo stole the cup, Smaug issued from the Gate in a fury, the waters rising in fierce whistling steam as he soared into the air, blazing, to hunt the thief. The Gate thus became the symbol of the dragon's dominion and the source of his raids.
The Siege and Fortification
After Smaug's death, Thorin and the dwarves fortified the Front Gate against the approaching armies of the Lake-men and the Elves. They built a high wall of squared stones laid dry across the opening, with holes for shooting and a small low arch for the stream. They also altered the riverbed to create a wide pool before the wall, making approach possible only along a narrow ledge. From behind this wall, Thorin parleyed with Bard and the Elvenking, refusing their demands for a share of the treasure. The Gate became the focal point of the siege, with the dwarves holding out while Dain's army marched from the Iron Hills.
The Battle and the Sortie
When the Battle of Five Armies began, the dwarves of Dain arrived and fought alongside the Elves and Men against the goblins and Wargs. At a critical moment, when the defenders were being overwhelmed, Thorin led a sortie from the Front Gate. Part of the wall fell outward with a crash, and the King under the Mountain and his companions leapt out in shining armour, rushing into the fray. Thorin wielded his axe with mighty strokes, driving against the bodyguard of Bolg, but he was eventually surrounded and fell, pierced with spears. The Gate thus witnessed both the last stand of the dwarves and the death of their leader.
Aftermath and Legacy
After the battle, the dwarves remained in the Mountain under Dain's rule. The Front Gate, though damaged, remained the main entrance to the restored kingdom. The Elvenking laid Orcrist upon Thorin's tomb, and it is said that the sword gleamed ever in the dark if foes approached, so that the fortress could not be taken by surprise. The Gate, once the dragon's lair, became the symbol of the dwarves' return and the new peace that followed the war.