A/N: Written for the Diversity Writing Challenge, L17 - write and post one chapter a week until you have written 100,000 words. This is like my fourth attempt so let's see how long I last. Longest so far is about 16k, so wish me luck!

About the AU – one of the main things that have changed are some characters ages in relation to others and to the general timeline. For example, Roy is 23 in 1908 (which agrees with canon, since he was 20 in 1905), but Ed is 16 (when he was in fact 16 in 1914 and should be 10 in 1908). The rest of Mustang's crew save Hawkeye also keep their 1914 ages. You'll see Riza when she shows up in a few chapters. The other thing is the ranks/some past experiences – Ed and Roy have switched…which is really the point of the age-scramble above. The atmosphere in Mustang's office was rather unofficial to begin with, but the power switch will still change things, and I'll be dipping my fingers in and messing things up too. :D

Enjoy!

Flame and Fullmetal

Chapter 1
Meet and Greet

Roy Mustang was quite proud of himself, achieving the rank of major at twenty-three years of age. He owed that to a number of things: the lifelong friends he made in the cadets, Berthold Hawkeye's teaching's, Riza's trust, and the simple luck that saw the State valuing offensive alchemy after the Ishbalan Civil War.

Too bad he'd been preparing for the state alchemy exam in 1908, some whispered in passing as he strode through Eastern Command on his first day. Might've made it Lieutenant Colonel, they whispered. If he hadn't been killed instead was the unsaid afterthought.

But achieving the rank of Major at twenty-three was impressive in and of itself.

He hadn't realised at the time that he'd been assigned to the one person such pride meant nothing to.

Instead, he paused outside a door, double-checked the address and his dress (specifically the pocket watch clipped to his belt and stuck in his pocket, and the stars on his shoulder), and knocked on the door.

'Don't you have an arm?' was the sharp retort. 'Open the door yourself.'

Roy blinked at the wood, then obeyed, twisting the knob. The door stuck a little, and he gave it a firmer nudge. There was a snicker inside. 'Boss just kicks it.'

Roy looked towards the base of the door. Indeed, there were marks near the bottom. Still, kicking the door was…undignified. And for all he knew, that was his new workmates trying to get him into trouble. He pushed instead.

The door creaked open and he entered with a salute. The snickering started up again: a blond man with a pen between his lips (and he looked like he'd rather have a cigarette there instead) and a smaller, plumper man with a tuft of orange hair. And then there was a kid in a red coat who didn't even look old enough to be in the military building, let alone in one of the offices, and yet he seemed perfectly at ease with where he was. In fact, he looked amused as well.

'Don't bother with that rubbish,' he said. 'It's painful just looking at an old man like you saluting me.'

'Old man!' Roy exclaimed. That was a sharp blow to his pride in more than one way. 'I'm twenty-three years old.' He paused, then added, somewhat unnecessarily: 'and a Major.'

'And I'm sixteen and a Lieutenant Colonel,' the boy replied, uncrossing his arms and leaning back on the large desk at the back of the room. 'Your point?'

Roy didn't have a reply to that, because his brain was still trying to process how the boy with the gold ponytail and white coat who was shorter than him and younger than him was a Lieutenant Colonel. And how did one even enter the military at sixteen? He was a kid. Legally. 'What the heck?' he asked, blinking. 'Is this some initiation joke?' Then again, there was that urban legend around the east about a kid with a metal arm and leg accompanied by a walking suit of armour…

'Nope,' said the man with the pen in his mouth. 'I'm Jean Havoc, by the way. Second Lieutenant. And that's Breda. Falman and Fuery are picking something up from the library –'

The door creaked open again and two men entered, each's chest obscured by a pile of books. 'Here you go, Edward,' wheezed the one with white hair. 'Where do you want them?'

'On the desk Falman,' said the kid in the red coat.

Roy made a mental note, just in case it wasn't a prank. Falman deposited the stack of books. They were all about alchemy. Biological alchemy. Roy looked back at…Edward. He held himself confidently, almost arrogantly, even while leaning on the desk. He had a silver chain from his belt to his black leather pants. That could be the State Alchemist's pocket watch. He was wearing white gloves – but Roy couldn't make out any transmutations on them. Then again, the urban legend said the kid could clap and produce alchemic reactions without a transmutation circle.

'What?' the kid raised an eyebrow. 'Don't believe me?'

Roy collected himself. 'Major Roy Mustang, Flame Alchemist. Assigned to Lieutenant Colonel Elric in Eastern Command.'

The boy smirked and pushed himself away from the desk, striding past the smaller ones. He walked confidently as well, though there was something odd about the footsteps against the wood. Hard, then soft. Hard, soft. The boy stuck out a hand. 'Edward Elric, Fullmetal Alchemist. And some paper pusher decided to stick me with an extra star.' He looked sour for a moment, but the expression was gone when Roy blinked.

He took the hand and shook it, released it – then froze. 'Automail!' he exclaimed. The kid with the metal arm and leg. The Fullmetal Alchemist.

'Slow,' the boy remarked, spinning around again. 'You've got the big desk at the back. I'm borrowing some of it for the books. We'll talk about ground rules after lunch.'

'After lunch,' Roy repeated. 'What am I doing before then?'

Edward threw his coat onto the pile of books. 'We're sparring.'

'Not in here,' the black haired man with glasses squeaked. 'You don't want Lieutenant General Grumman mad again.'

Edward laughed. 'He's just putting on a show. He doesn't really mind.'

'But still –

'By the way,' Breda cut in. 'Fuery, fork it over.'

'Fork what over?' Fuery's brow scrunched.

'Our winnings.' Breda rolled his eyes. 'How long it took for the newbie – I mean, Major – to recognise the boss.'

Roy was embarrassingly relieved to hear himself being referred to as Major, because this office didn't seem to follow any Military protocol. Okay, the others were wearing uniforms even if they weren't buttoned up to the chin like they were supposed to be. And Lieutenant Colonal Elric (it was weird calling a sixteen year old that) was wearing his pocket watch and maybe those gloves were the military issued ones, but aside from that…

'By the way.' The gloves came off next, then black sleeved shirt, leaving a sleeveless shirt underneath and exposing the automail arm in its full glory. Roy tried to discretely stare. He'd seen automail before, but not on someone so young.

If that kid really was his commanding officer, he was going to have to get out of the habit of calling him kid.

'Don't call me Lieutenant Colonel unless someone ranked Colonel or higher is listening in. And isn't old man Grumman. Got it?'

'Got it…' What did he call him then? Kid was at the tip of his tongue but entirely inappropriate when the kid in question was a rank higher than him and his commanding officer. 'Sir?'

'Don't call me that either.'

'Try "boss",' Havoc suggested. 'That's what we do. Or Edward, if you're all prim and proper like Falman.' He ignored the exclamation. 'Or Fullmetal if you're big on alchemy titles – guess you'd be, being a State Alchemist and all.'

No way was he calling his commanding officer by a nickname like "Ed". At least, not to his face. He'd go with Fullmetal for now, he thought. It didn't regard rank but at least it was respectful.

He was all messed up already, and he hadn't even survived half an hour yet.

'You going to spar in that?' Fullmetal asked, raising an eyebrow.

Roy stared at himself, all dressed up in proper military wear, then shrugged and started unbuttoning the jacket.

.

Sparring with his superior officer wasn't how he'd planned on starting his work at Eastern Command. Winding up with one of his precious gloves torn during the spar was also something he hadn't expected. But Fullmetal had proved to be a formidable opponent.

Roy guessed the kid had to be tough, to hold the rank he did at his age. Or to even be in the Military at that age. He'd been quick to get Roy's timing, dodging the initial balls of fire and transmuting blocks from the earth to block or propel him away from the rest. Roy got to see the circleless alchemy in action there. A sharp clap, hands placed on the dirt, and a column would be rising out of it. The transmutations on the other hand were basic – at the beginning.

Things got interesting when Fullmetal started giving his columns hands and legs and sending them after Roy. Things got even more interesting when he transmuted his automail – and, ultimately, that was what clinched him the win. Roy hadn't expected the hand swinging at him to turn sharp, so he'd ignored it in favour of preparing his next attack.

And he took too long getting the other hand out of his pocket.

That hadn't been confidence, or arrogance. That'd been keeping a secret weapon in reserve – but that hadn't gone exactly as planned.

But Fullmetal didn't comment much, once they were done. He just nodded to himself, then pointed out the showers and went to take one himself.

The others just clapped him on the back and said that was just how the boss did things.

Roy wondered if he'd managed to make an utter fool of himself in the first half day. At least the having lost to a kid had less sting when the kid held a rank higher than him.