With the death of both the Kings at the Battle of Dale, the armies were leaderless and spread out. Yet they continued to hold the gates of Erebor, and keep the orc hordes out of the Halls of Thorin.
So it came to pass that Legolin desended into the depths of the earth in quest of Orcrist, the legendary sword of Thorin Oakenshield. Although an elf, he walked unafraid in the dark places of the world. He overcame the spirits of the those long dead and won Orcrist from the Tomb of Thorin.
With Orcrist in his hands Legolin returned to the fray. Through the power of men and the strength of dwarves and the ferorcity of Legolin, the enemy was repulsed from the gates.
As the orcs fled from the light of Orcrist, Legolin broke out from Erebor, slaying on the left and the right. So he returnd to his father Thranduil of the Wood Elves and delivered Orcrist to him. It was with that blade that Tnranduil was finally able to break the siege of his realm.
As for the Men and Dwarves of Erebor, they held the gates for the rest of the war and no orc could penetrate. Finally at the end of the war the siege was broken with the aid of King Thranduil and Celeborn of the Goldenwood. So the Lonely Mountain became the site of the a second great battle of Men, Elves, Dwarves, and Orcs, but that is another story.