This story ties in to Shadows' Call

“The Brute, The Insubordinate, The Slacker, and The Thief! Princess Celestia, with all due respect, what in your own name made you think this project was worth any time or effort?”
“That is simple Colonel, they are effective. You showed me their exercise reports yourself. Besides, I wasn’t really looking for an ‘orthodox’ team.”
“Permission to speak Ma’am?”
“Blanket permission to speak granted Lieutenant Snowfall. You work the most closely with them, I would consider your input invaluable.”
“Thank you Ma’am. I guess if you really want to understand how truly far they’ve come, you have to go back even further than when you picked them up and put them together. If you have the time, I want to tell you both exactly how and why each of my ponies wound up in the position that let you form Spectre Squad…”