Here's another switched!au because I love them and should write them more often! Possible TW for violence and mentions of whump.

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Bucky Barnes was never one to give up; as Captain America, he couldn't afford it, couldn't allow himself to waver for even a second because when he wavered, when he couldn't do the job he swore himself to do, people died.

People like Steve Rogers.

Bcuky shook off the memory of him and pushed onward, teeth grit before throwing himself into the fray.

Bullets and blasts of energy were flying through the air. With wide eyes, Bucky watched civilians get vaporized, soldiers, guards -- he leaped in, shield at the ready.

Minutes later, spinning to check around himself, Bucky found himself surrounded and alone. He rolled his neck and studied them all, the twenty-something guns pointed at his face.

"Evening, fellas," he mused before jumping into action, dodging and weaving and fighting viciously to survive with as little damage to the general public as possible.

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Hours later after the paperwork and after Tony blathering on about politics and their civil duty, Bucky was finally alone. He cringed as he passed by a mirror to see that he was as roughed up as he felt. Smaller cuts were closing before his eyes but the bigger wounds would have to take a while.

Deciding not to do anything about it, he went straight to his room, depositing his shield and helmet along the way, and flopped onto his bed. He stared idly at the ceiling, replaying the mission over and over again, perfecting it mentally and giving up on that venture because it was a pointless one.

He answered Sam's incoming call with a groan. "Hey, Sam," he sighed and pushed himself into a sitting position. "Tony send you after me for somethin'?"

"Not exactly." Sam's voice was casual enough but the tone he was talking in made Bucky think something was up. "So, I found him," he continued in that same too-casual voice.

Bucky got up. "Where?"

"Actually right across from me," Sam mused, staring intently at the crouched shadowy figure perched on the faraway rooftop. He shifted where he kneeled as silently as he could. "Corner of 5th and 6th."

Bucky was already hurriedly pulling his boots on, grabbing his shield.

This unnamed Winter Soldier had been a thorn in their sides for the past couple years, now. Always pursuing him, each fight coming away more violently scarred than before, Bucky could tell that their cat-and-mouse game was coming to a close.

As he straddled his motorcycle and kicked it into gear, his thoughts remained on the soldier with a mess of shaggy hair, mask fixed tightly onto his face, glasses obscuring the person. The metal arm, ruthlessly powerful and dangerous.

He wasn't going to lose him again.

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Bucky sprinted up and hurled his shield as hard as he could, hoping to catch the soldier off-guard, but instead the soldier caught it; threw it back to him with enough force that it pushed Bucky physically backwards when he caught it.

He looked up to see a metal fist flying his way, raising his shield in the nick of time to block it. Metal on metal rang through the air and Bucky flinched at the abrasive sound. Sweeping his leg around he intended to get the soldier down, at least, because a downed opponent is as good as dead -- but the soldier had training.

They stared opposite of each other for a moment, and Bucky quickly regarded the soldier's stance; he was going to dive into an attack, and Bucky had to be ready.

When the soldier sprinted at him, Bucky spun, grabbed him and flipped him over himself, slamming him into the pavement. Whirling around, Bucky raised his fists and mentally braced himself -- but the attack didn't come. The soldier was getting to his feet and pressing a hand to his face; his goggles had been knocked off.

For a second, Bucky could only stare. For a second he saw Steve Rogers in the now-visible, dull blue eyes, and he was powerless.

His shield slipped to rest on the ground. A million thoughts were swarming him but over it all he knew that he couldn't fight back.

Captain America, a man who never gave up, lowered his shield and stared at the man he'd let down -- the man he'd loved.

"Steve..?"

The soldier faltered and Steve stumbled a step backwards. "Who the hell is Steve?" His voice was a murmur, he sounded more confused than anything, and took a second to gather himself.

Bucky could've had him in that second. Here was the soldier in front of him, defenseless, had killed hundreds -- and he couldn't do it. He couldn't do it.

Bucky relented.

The soldier gave an imperceptible shake of his head and pulled a gun from its holster; Bucky didn't react, too helpless to fight back because how was he supposed to fight back now?

All he saw was Steve Rogers ready to kill him, and then a shot from behind him slamming into Steve's shoulder. Staggering from the blow, the gun fell from his grip, and with one last look he was gone.

Bucky felt like fainting but he forced himself to run after him, jumping onto the ledge of the building and looking down and around -- no trace of him.

"You didn't get him. You could've easily taken him down, why didn't you?"

Sam walked up behind him, eyeing where the soldier had disappeared to as he holstered his own weapon. He glanced at Bucky, white as a sheet -- as if he'd seen a ghost. "Why didn't you?" His voice was softer.

Bucky swallowed the knot forming in his throat and blinked. "Couldn't," he murmured and finally met his gaze. "Sam, it was him."

"Him..?"

Bucky stared back towards the dark city and clenched his jaw. "Steve."

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Their second run in and Bucky tried to fight back; lives were at stake and he hated himself for every hit Steve took, especially when he aimed a blow at the bullet wound in his shoulder. Once again Steve fled the scene before Bucky could get him under custody and he wondered himself if he was actually trying more to not hurt him or to get him in custody.

It was their third and final fight that did it.

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Half an hour had passed and Bucky was in poor shape; he'd abandoned his helmet, shield loose in his grip, breathing harshly. It was difficult to ignore the stabbing pain in his stomach, a pain that threatened to make him pass out, but it was almost more difficult to see Steve look frightened about coming out of this alive.

"I'm not gonna fight you," Bucky panted, staggering with the jolt of the airship that was mere moments from crashing into the freezing water below. "You're my friend." Meeting his eyes was painful; he saw him and he saw him falling to his death, the memory of how he'd lost him constantly playing on loop in his mind.

Steve looked resigned, now, just stared at him. Bucky took a step closer. "Your name is Steven Grant Rogers, you -- "

The tackle came out of nowhere and Bucky let the shield slip from his hand.

"You're my mission."

Bucky didn't have time to brace himself before the metal fist slammed repeatedly into his face, and he was barely conscious. When he opened his eye, Steve was staring at him, and his once dull blue eyes were bright with tears.

"Then finish it," Bucky murmured, weaker than he'd wanted. "'Cause I'm with you 'til the end of the line."

Steve relented and an indescribable look passed over his face. Fear? Horror? Bucky didn't have time to analyze further before the glass broke beneath them and together they crashed into the Potomac.

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Bucky woke briefly on the shores of the Potomac and saw the blurry figure of Steve Rogers standing there, then kneeling near him -- not too close, but close enough to tell if he was still alive.

Steve watched with surprising concern, making sure Bucky was breathing. "Steve... " his eyes fluttered closed again and Steve sat back on his heels, taking a slow breath in. He watched his chest rise and fall for a second longer before standing, making himself scarce once again.

When Bucky woke up in the hospital he knew who'd saved him.

He'd make sure to return the favour.

"You don't have to come with me," he said quietly to Sam, looking towards the ground. Sam studied him evenly.

"I know." He paused, cocked his head. "When do we start?"

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This got long and I wanted to do it justice so that's why it's late, so my apologies! Lemme know what y'all thought :)