John was a soldier.
An army doctor counted as a soldier after all, and he had been in combat.
He liked pulling rank, it sent a thrill through him. He still remembered bandying his title about when they were sneaking into Baskerville with a sort of fondness. In fact he'd been dying for a chance to order someone around ever since, carrying with it a sort of guilty pleasure.
So when he'd woken up that morning to see Sherlock's lab equipment spread all over the flat, the detective himself blatantly ignoring John's displeasure at the mess, he decided that it was his turn to perform one of Sherlock's infamous "social experiments".
"What the hell is going on?" John half yawned half yelled in frustration.
"Comparing the abilities of the acid used by the alleyway murder to the acid samples collected at Lestrade's crime scene yesterday." Sherlock replied without looking up, perched on his chair clad in his pajamas with a test tube dangling from his long pale fingers.
"And you need your lab stuff all over the bloody flat for that?" John sighed.
"That was from yesterday's experiment. I can't be bothered with it right now." Sherlock continued to look away from John and focus instead on his experiment. That's when John really snapped. Stomping forward he grabbed Sherlock's face and yanked it upwards.
"Look. Me. In. The. Eyes." He growled. "I'm not some idiot you can shut up with your babbling. I deserve more respect, and you are going to give it to me right now."
Sherlock's wide eyes were the only indicators of surprise, the rest of his body remained relaxed and unchanged from it's earlier position. Sherlock took a moment to recover and then replied as sarcastically as ever.
"...meaning?" he asked with a bored expression.
"I didn't give you permission to talk." John barked, and Sherlock's mouth snapped shut. "Better. Now you're going to clean up your shit in record time or else I'll punish you. Understand?" John didn't know what sort of punishment he could give to his flatmate or if he even could punish his flatmate, but hell he was on a roll and it seemed to be working because Sherlock actually leaped into action, sullenly putting lab equipment back where it belonged. Once he had finished Sherlock turned back to John with a dark yet confused expression, as if he was angry at being ordered about but confused as to how he let himself get ordered about.
"I want it like this everyday, you got that? If you're done with something you better put it away, and I'll tell you when you're done with it without any arguments from the likes of you." John smirked slightly, a little bit embarrassed at having let his anger get out of control like that.
His attitude seemed to be having a strange affect on Sherlock. The detective was silent for one thing and that was always strange. The detective was studying John with an intensity he'd never seen Sherlock use on him before. His eyes darted all around John as if trying to look inside him and see where this sudden dominance came from. Then Sherlock looked back into John's eyes.
"Anything else...sir?" He replied playfully.
Oh God that sounded good.
John found himself longing to hear Sherlock say it again, so he asked.
"One more time?"
"I said, anything else...sir?" Sherlock seemed to be catching on, delightedly so in fact. "Or should I call you Captain?"
"You'll call me what I want you to call me." John ran a hand down Sherlock's hip, eyes gleaming. "Sir will be sufficient for now."
"What are your orders, sir?" Sherlock took extra care with that word...sir, and he held eye contact with John and let only the shadow of a smirk come over his face. John said only one word in response.
"Now." He pulled Sherlock in close and left bite marks on his neck, silencing the detective's whimpering with a growl. The two fell onto the couch in a tangle of limbs. At first Sherlock tried to straddle John but John flipped him over and pinned his hands over his head, taking extreme pleasure at watching Sherlock pout and squirm.
"Not today. You're going to do what I say. Now call me sir again."
Sherlock smiled and let out a dramatically pathetic: "Sir."