I guess this is my idea about why Balin seems less inclined to revenge and fighting than some other dwarves. I've kind of followed the book timeline more than the movies, so Thror's murder by Azog was what sparked the Goblin War, rather than occuring during it. And Balin is also quite a bit younger here. I did pinch the last line from the movie though!

Balin fought by his father's side. He'd fought before, skirmishes, night raids, but never a battle. Never a war. A war for the honour of Dwarves.

The goblin tunnels were thick with blood and shouts, the clash of metal and stone. Fundin lead their company, his huge axe cleaving every orcish foe in his path and Balin was by his side. He was keeping pace, for every goblin his father felled - Balin got one too. The victory, the honour coursed throught the young dwarf's veins and gave his sword arm more power. They were winning, even now the goblins turned and ran into the dark tunnels before them. Fundin raised his axe and pursued them with a cry and Balin raised his sword to do the same-

BANG

-he lay on the tunnel floor, ears clanging, rocks and dust and darkness surrounded him.

'Get up! GET UP!'

A strong hand hauled him to his feet. He peered in the gloom and was suddenly blinded by a tinder strike and a torch roaring to life. It lit up his father's face, staring grimly over Balin's shoulder. He turned to see what his father looked at and his jaw dropped.

A mountain of boulders blocked the way they had just come. More than half their company was missing.

'A..a cave in?' Balin stuttered but Fundin shook is head in fury.

'Explosives. Damn these goblins, could've brought the whole mountain down on themselves as well as us.'

Balin gauped. Working with explosives took a dwarf decades of training and even then they were only used with the greatest caution and planning. Balin was about to say this when his father turned to him with a grin and grasped his shoulder.

'They're getting desperate. That means we're winning. Come on, help get the remainder of the company on their feet, we can't lose the advantage now.'

Balin turned from the pile of rubble, trying not to think about the dwarves buried under it. We can come back later and search for survivors, he told himself. We can come back after we've won. He picked up his sword and went to help the others.

The dwarves tramped on through the tunnels, ignoring ringing ears and aching bodies, ignoring the fighters buried behind them. They heard only the distant yells of goblins and thought only of revenge. They marched faster through the deep tunnel, following the only route the fleeing goblins could have taken. They followed it until their way was again blocked.

Smoke-blackened planks and iron bands formed a narrow door. Their foes last defence. Fundin raised his axe and roared.

'BREAK IT DOWN!'

The surviving dwarves obeyed and as the door splintered to nothing under their weapons they were greeted with blood curdling screams. Balin actually stumbled backward as goblins poured out of the destroyed doorway. Their eyes were black with fury and their teeth bared. They seemed to have few weapons but attacked with enough blood thirst that it didn't matter. Balin raised his sword in terror and swung.

Beserkers. They had to be. The most fearsome, souless of goblin warriors. The goblins before him fought even as they died, no matter what injuries they sustained they continued to fight. Dread seaped cold through his blood. But a glance towards his father showed Fundin standing proud and fearless, with a glint of victory in his eyes as the goblins fell under his axe. Balin fought on and soon the company had pushed through the door way and into a cavern.

It was filled with goblins. But these were not the berserkers the dwarves had successfully hacked their way through. Weaker goblins, cowardly and small that fled more often than fought. It was a rout.

Panting and shaking with fatigue, Balin dropped to the ground beside an old dwarf. The cavern that had been filled with cries and the clash of weapons was almost silent as the company surveyed the field of their victory. Balin felt utterly spent but the knowledge that they had won not just a battle but another step towards the revenge of their king kept a grin on his face. He turned to the warrior who sat beside him.

'It was close there, I thought. Not the last lot, that was easy but the ones at the door. Beserkers, do you think?'

But the dwarf shook her head, her face grim and streaked with blood.

'Parents, I think.'

Balin froze. His body froze. His mind froze. His heart froze. The old warrior nodded slowly.

'You are right in a way. They fought harder than any beserkers I've faced.' She sighed and looked down. 'I don't blame them, who wouldn't fight to the death to protect their children.'

'Children?' Balin gasped. He had never thought of goblins having children. Yes, of course they bred, but surely they didn't have families. Surely goblins didn't care like dwarves did. The old dwarf fixed him with a cold stare.

'Yes, children. Why did you think the little ones were so easy to kill?' Balin broke her gaze and found his eyes coming to rest on his father. Fundin, leader of the company. His hero. He had followed where ever his father lead, without question. But now a question filled his mind. The old dwarf voiced it.

'Did he know? Yes.' Balin turned to her, eyes stinging with tears.

'Of course he knew. He has a job to do. Defeat the goblins. If we don't kill them all, they will come back. They will come back and destroy our homes and our people as they have done for centuries.'

'And as we have done for centuries.' Said Balin coldly, suddenly he saw from a new perspective. The dwarves were the invading force, destroying homes and families. Yes, they fought for revenge, for the honour of their dead king. But now there seemed more important things.

Life. A life of peace and plenty. That seemed to be worth all the gold, all the revenge and honour that could be had.