The Dwarves in The War of the Ring

Some may say that the dwarves did nearly nothing in this war, with only Gimli truly participating. However, the dwarves perhaps won the war before it even started.Shortly before The Hobbit, which was about 60 years before The War of the Ring, there was a large war known as The War of Dwarves and Orcs. This started when Thorin II Oakenshield's grandfather Thror gave his ring of power to his son Thrain and set out for Moria with a dwarf named Nar. When they arrived Nar hid outside and Thror was captured and tortured. The orc's king named Azog branded his name with runes onto Thror's forehead and thrust it to Nar, who was spared to send a message to the dwarves, saying never to return to Moria. Nar did this and for three years the dwarves gathered their strength. They wanted vengeance against the bane of Thror for being so disrespectful to Durin the Deathless' heir. The dwarves from all seven of the founding fathers soon attacked. They attacked and pillaged every orc camp in the Misty Mountains, searching for Azog. They eventually reached Moria and the Battle of Azanulbizar was fought. In this Dain II Ironfoot (who later became the King Under the Mountain in Erebor) slew Azog by cleaving his head. Most of the orcs/goblins in the north were wiped out in this fight. 

 http://lotr.wikia.com/wiki/War_of_the_Dwarves_and_Orcs

Now we come to The Hobbit. During The Battle of Five Armies most of the orcs/goblins had repopulated and they had nearly returned to there former strangth. However, in this battle between the armies of the goblins and wargs against the men of Lake-Town, the elves of Mirkwood, and the dwarves of the Iron Mountains led by Dain II Ironfoot, about three fourths of the goblins in the north were slain, leaving their numbers diminished. Also, thanks to Bard of Lake-town and the dwarves for giving him the oppurtunity (though it was because of Bilbo that he knew of Lake-Town and because of him that Smaug was able to be defeated) to slay Smaug the Golden. If Sauron had been able to control either of these The War of the Ring could have ended in the north, but they were, and The Necromancer (Sauron) was drivven out of Dol Guldur in Mirkwood and he was forced to flee to Mordor.

So, without the khazad, all hope would have been lost. Baruk Khazad! Khazad ai-menu!