Part 1; A Marine with a dark past is dropped into Equestria during Twilight and Flash Sentry's wedding (for no good reason I will now duck gunshots) in Sweet Apple Acres. Said soldier falls in love with Applejack and earns the eire of Blueblood.
Part 2; Cpl Smith and Applejack have to deal with the stress of pregnancy as more soldiers of various time periods, nationality, and rank arrive in Equestria.