How does the entry of the goblins into the Battle of the Five Armies affect the warring parties and why?

Thorin Oakenshield, Bard of Lake-town, and the Elven-king
were locked in an impasse.  Bard and the Elven-king had formed an alliance in an attempt
to persuade Thorin to repay the people of Lake-town for all the damages that Smaug
caused the night the dragon left the Lonely Mountain and destroyed most of the town.
Thorin staunchly refuses to give any of the treasure away, and even with Bilbo's giving
Bard the Arkenstone as a bargaining chip, the dwarves still will not come to a
reasonable agreement. 

The tension escalates as Dain
Ironfoot, Thorin's cousin, arrives and sees the camp of men and elves entrenched at the
foot of the mountain.  Both sides are ready to attack--and then Gandalf cries out "Dread
has come upon you all!" (251) The Goblins and Wargs arrive, swiftly changing the outcome
of Bard's siege.

The Battle of the Five Armies had the
positive side-effect of making the elves, men, and dwarves join forces to defeat the
Goblins and Wargs.  At the end of the battle, the goblins' numbers are greatly
diminished, and the dwarves, under Dain's leadership after Thorin's passing, do make
amends with Bard and the Elven-king, thus resolving the original
conflict.