Summary: The moment Dean became the wall between his brother and absolutely everything else. Pre-series.

Author's Notes: I hope John's a sympathetic character in this. I think Sam was Dean's the moment John put him in his brother's arms, but this is maybe the point where Dean decided he needed to protect Sam from everything, even things he hadn't seen as threatening previously. Enjoy!

Defined

John regretted it the second it happened. But regret can't take it back.

He watched his youngest, fourteen a week ago, struggle up to his hands and knees, spit blood on the ground, and stay there, swaying slightly. John just stared at him. Both too shocked to move.

The sound of Sam's head rebounding as it hit the one patch of concrete where they were training made him sick.

He was pushing Sam too hard and he knew it. He hadn't even taught him the proper blocks for the way John had gone after him, but his youngest could make him so angry sometimes and he had just lost his control.

Sam had been fighting him on absolutely everything since he's hit thirteen. He'd gone to soccer practice this afternoon instead of training with Dean even though John had told him a week ago to quit the team, that there was no time and they'd only have to move again anyway. That was the reason he was sparring with Sam now when the sun was more gone than not.

John loved Sam, loved his boys, he did. But Sam had to be tough. Had to be. For himself, for his brother, for the world, if the demons were to be believed.

John ran a hand over his face and, after a moment, reached out to help Sam up. His flinch of fear was quickly disguised as anger as Sam swatted his hand away.

John didn't offer again.

Sam didn't say a word as he stood up and squared his shoulders. He never looked at his father, never said a word as he started back toward the house they were squatting in.

John watched him go feeling something dire had shifted. That this was a moment that would define them.

And he had never screwed up so badly.

Dean looked up, annoyed as all eighteen year olds are, as his brother came in and went straight for the kitchen.

"Hey, you're back early. You didn't run out on practice again, did you?" No bitchy remark from his brother and Dean's brow furrowed. He sighed. "Look Sam, I know you think he's being tough on you, but he's only trying to get us ready, you know? Make sure we can handle ourselves."

Dean watched Sam's back to him, standing at the sink, and started to worry at the silence. He decided he might need a soft touch right now since something was definitely off with Sammy. Sighing, Dean put a hand on Sam's shoulder and turned him around.

He'd never felt so cold an anger before.

Sam wouldn't look at him, enraged hurt in his brother's eyes, wounded pride. Dean made sure to steady his voice before he crouched down to look at his brother's face.

"…Did dad do this?" Sam didn't answer and Dean clenched and unclenched his jaw. "Come on."

Sam followed where Dean led in an entirely too subdued way. When he got Sam into the bathroom, wet washcloth in hand, he made sure to stay on level with him.

He was exceedingly gentle in the way he tended to Sam's busted lip, his rapidly bruising cheek. He helped Sam wash the blood out of his mouth at the sink, watching the way Sam swayed slightly. Dean noticed the way his little brother's eyes kept drooping, the pupils uneven, and cursed when the hand he placed around the back of Sam's head came away a bit bloody.

"Come on." He led him again, this time to their bedroom, and sat him on his bed. All the fight was gone from Sam. He was just…tired. In the way no fourteen-year-old should ever be. Dean forced a smile into his voice and turned to their dresser. "We'll get you into some more comfortable clothes, yeah? Maybe I'll cook dinner tonight, even if it is your turn-"

He turned around, clothes in hand, to find Sammy already curled over on his side, back to Dean, utterly exhausted. In the same everything's-fine-voice, he kept talking as he pulled off Sam's shoes and shimmied the covers out from under Sam to pull over top of him.

"Okay, just sleep. I'll wake you up in an hour, okay?" Sam mumbled something at him unhappily. Dean rolled his eyes. "Yeah, yeah, I wasn't really asking." He patted his little brother's shoulder comfortingly and Sam seemed to relax. "I'll take care of this." The tone was light, the words deadly.

Dean heard the door open and close, softly, like Sam did when he was sneaking off to soccer practice or to rehearse for a play. He took a deep breath before turning out the light in their room and shutting the door gently behind him.

He found their father pouring a drink from the mantle stash. Deceptively calm, Dean took the glass from his father's hand and placed it back on the mantle. John wasn't looking at him and he wasn't looking at John.

"…If you ever lay a hand on him like that again, you will never find us."

Finally looking up, John saw murder in his eldest's eyes. He didn't even try for an excuse, just nodded almost imperceptibly. Even as enraged as he was, Dean saw the shame in his father's expression. That may have been what kept Dean from slugging him.

Dean turned and walked back down the hallway without another word, back to the boy's room. He had a little brother to watch over.

This was the defining moment John had felt was coming. A moment when John saw everything clear, saw the status quo that had really always been there, finally solidified.

Dean had always stood between his little brother and the rest of the world. From now on, John would be part of that world. And, though it broke his heart, John thought maybe that's just the way it always had to be. Maybe Sam and Dean against the world was the way it should be.