Andre Norton 
The Time Traders [EPUB ebook] 
With linked Table of Contents

Ross Murdock had a choice, prison or volunteering for Operation Retrograde. He didn’t like those choices, not at all. Unwilling, he volunteered to go back in time and become a foot soldier in a time war. It was a choice that would change his life and shape his future. It was a war that had to be fought, and it had to be won.