You don't stop being a soldier because you got wounded in battle. Not every battle is physical, wounds aren't necessarily external, and soldiers do whatever it takes to get through. Even when they accidentally time travel.

Fred went into a coma after the Battle. He was unconscious for days, and when he woke up he believed in a world that didn't exist. One that will forever change his and Hermione's life. "If he says something barmy you want us to go with it?" "Precisely!"

Complete. FWHG. Hermione and Fred accidentally go back in time to the Marauder's Era when a potion explodes. Hilarity ensues when Fred creates their cover story.

When Fred Weasley finds out he's betrothed he's desperate to get out of it. So he enlists the unlikeliest person for help. Fred/Hermione