What was the Hwarang's Role during Silla's plight to unify the Peninsula?

Hi all!

I have been writing a historical fiction book about the Three Kingdoms Period for some time now, specifically the years leading up to Unification.

(To clarify, the book will end in 668 A.D. after the fall of Goguryeo, not 676 A.D., when Silla successfully expelled Tang from the peninsula.)

The book is centered around a host of characters who are supporting Silla's war efforts in one way or another. The main/side characters are supposed to be Hwarang who enlist in the military and aid through various means (combat, advisors, strategists, etc.) There are a few real people I am incorporating in the narrative: Kim Yushin, Kim Won Sul, Seondeok, Jindeok, King Muyeol and Munmu, to name a few.

My main concern with the book is the relevance of the Hwarang during actual combat. From the research I've conducted, there are mixed signals on whether or not Hwarang played a large part in military efforts. Some people claim that they were only young aristocrat men who were trained to be effective leaders and scholars. Others say they only participated when Silla started to be more involved in conflicts leading up to Unification (and even then, their role was minimal with few exceptions like Yushin). Then there is the argument that they were trained in martial arts and combat and were a heavy influence in the military.

So what was the Hwarang's actual role? Would it be unrealistic to have my characters partake in majority of the battles? The book will have two main characters whose primary role is assisting in combat and medicine, but now I'm doubting how realistic this is.

While the book is labeled under fiction, I do want to try and stay true to the history as much as possible. I've tried to do as much research as possible myself, but I wanted to reach out here to see if anyone knew anything!

And if you have any fun facts about this time period, I would love to hear it! The book takes place from 642 A.D. - 668 A.D. but I've done research from roughly 500 A.D. - 800 A.D.

Thank you in advance! Sorry if anything is misspelled or wrong.