For 675 days, he was arguably the most important man in America, responsible for the historic investigation into Russian interference in the 2016 presidential election. Yet through it all, Robert Mueller remained a mystery to many. In an era when leaks and backbiting are the political norm, the former FBI director distinguished himself with his reticence and determination to get the job done. The work has been both damning and detailed. Over the course of his Russia probe, Mueller won guilty pleas from the Trump campaign's chairman and deputy, the national security adviser, and a foreign policy aide, as well as President Trump's personal lawyer, Michael Cohen. Even more were indicted, including Trump's longtime friend and adviser Roger Stone. By the end, what started as a probe into the 2016 election had sprawled into at least 18 separate investigations, run not just by Mueller's team but by at least seven other prosecutors' offices as well. To understand the man at the helm of this historic inquiry, we need to go back to 1968, when, as a newly minted Marine lieutenant, Robert Mueller was shipped to Vietnam and put in charge of a unit that saw almost nonstop combat. Mueller joined their ranks during what would be the deadliest period of the Vietnam War. He soon convinced his wary men that he was distinctly different from many of the Ivy League leaders they'd had in the past. The men of Hotel Company were so tough and battle-hardened, they had earned the nickname Magnificent Bastards. Smart, decisive, and duty-bound, the future FBI director led his unit into some of the bloodiest fighting they would ever see, including the notorious battle for Mutter's Ridge. His time in the Marines would earn Mueller the Bronze Star and the Purple Heart and, above all, the trust and respect of his men. In the decades of public service that would follow, nothing would match that year of combat. "I'm most proud the Marines Corps deemed me worthy of leading other Marines," he says. In this first detailed account of the defining period in Mueller's life, Garrett M. Graff, author of the bestselling The Threat Matrix: The FBI at War, follows Mueller's journey from prep school to Princeton to the jungles of Vietnam. Groomed for service from a young age, Mueller approached his military career with a no-nonsense integrity that would become his trademark. He unhesitatingly led his men into battle and bravely pulled them off the field when they fell. Graff re-creates those terrifying moments and speaks at length with the survivors who, to this day, are awed by the actions of their young lieutenant. Ironically, most of those men were unaware that the man who led the Russia investigation is the same Robert Mueller who led them in battle. Even in the midst of the most controversial and high-profile investigation in American political history, Mueller prefers to keep a low profile and live by his nation's military principles: duty, honor, country.