By Jeff Horn, Jr.
“I prioritize self-development because I never want to look back and say, ‘I lost some of my Marines because I could not outthink the enemy.’” – Major General William F Mullen
I met Major General (MajGen) William F. Mullen in a Strike Cell during Operation Inherent Resolve in 2016. I was a junior US Army Captain in the 101st Airborne Division, and he was the Combined Joint Operations Cell Director and Target Engagement Authority for fires in support of Iraqi Security Forces. Little did I know then, but MajGen Mullen would profoundly impact my life. His basic message for leaders in the profession of arms was simple: Reading enables vicarious learning through the experiences of others, teaching leaders to adapt, generate intelligent decisions, and execute them more quickly than the enemy. The alternative, he explained, is to learn the hard way–through body bags of dead service members.
MajGen Mullen was brilliant, and his reading list shows why. From the mid-1990s to April of 2016, his reading list contained well over 2,000 books, averaging about 100 books per year. Because of his reading, he was particularly apt at explaining the parallels of centuries of history to present conflicts. He also had an uncanny ability to equate current events to the fiction literature classics. But the ultimate litmus test was in his decisiveness. He was reserved, but when he spoke, he was always prescient.
I once asked MajGen Mullen how he read two to four books a week. He replied, “I prioritize self-development because I never want to look back and say, ‘I lost some of my Marines because I could not outthink the enemy.’” MajGen Mullen viewed reading as a professional mandate. He devoted his time to developing the “5,000-year-old mind,” a term he used for those who studied the lessons learned from 5,000 years of recorded military history.
After the deployment, I kept in touch with MajGen Mullen. I invited him to Fort Campbell for a Leader Professional Development (LPD) session in 2018 and again for a virtual LPD session with the 3d Cavalry Regiment at Fort Cavazos in 2022. Besides that, our relationship spanned just three months–but no other individual has impacted me more.
In June of 2024, MajGen Mullen died of natural causes at the Twentynine Palms Training Center, a post he commanded less than a decade prior. As I reflect on our time together, my thoughts turn to what I’ve learned from MajGen Mullen. Specifically, I’ve emulated his daily disciplines to increase reading throughput. Through my own personal reading, I’ve also learned habits of thought that shape my understanding of myself and the world around me.
What MajGen Mullen Taught Me
MajGen Mullen taught me the importance of reading broadly. I typically read two to three books simultaneously, on topics including history, current events, leadership, fiction, military tactics (including doctrine), theology, and geopolitics/strategy. I don’t have a set rotation through different genres of books. Still, I always have at least one book directly related to the profession of arms, either through the lens of history, leadership, or military tactics.
MajGen Mullen taught me the importance of daily disciplines to enable reading during busy times. I read early in the morning before my day begins, and before bed at night. I also use the Kindle app on my phone to maximize reading opportunities whenever and wherever possible. Like MajGen Mullen, I often carve out white space in my day for reading. I find it helps my mind stay fresh and breaks the monotony of the day.
In the past few years, I’ve also supplemented reading with audiobooks–something that MajGen Mullen told me he engaged in frequently. Audiobooks have almost doubled my intake of books. They are incredibly efficient; I can learn while conducting mundane tasks such as laundry, dishes, driving, or during long runs.
My Reading Journey
Since 2016, I’ve modeled MajGen Mullen’s reading list format for my own reading list. I track each book I’ve read by genre and when I’ve read it. I also rate the quality of every book I read, and I periodically send out my reading list to subordinate leaders in hopes of inspiring them to read.
My reading has better equipped me to challenge false assumptions, changing the way I lead and influence others. Technologies have advanced, the internet has connected people across the globe, and information (and misinformation) is available at the cost of a few keystrokes–but humanity has not fundamentally changed. I’ve come to realize that the adage, “[t]here is nothing new under the sun,” is not just a platitude (Ecclesiastes 1:9).
Reading serves as a reminder for me to treat myself with kindness. Many of history’s most notable figures faced their own flaws, insecurities, and challenges. It’s important to be gentle with ourselves, taking lessons from our past while remaining present in the moment.
Moreover, reading reinforces my commitment to my core values. People who have succeeded throughout history often reached their goals through manipulation, dishonesty, and questionable ethics. It requires self-discipline to adhere to a strong moral compass, choosing the difficult right over the convenient wrong.
Finally, my reading illuminates the path forward, no matter what life has in store for me. It broadens my perspective, allowing me to explore possibilities amid uncertainty. At the same time, it helps me connect the dots in my understanding through the lessons learned from others’ experiences.
A Leadership Legacy
Marine Corps Doctrine Publication (MCDP) 7 (Learning), MajGen Mullen’s seminal work as the Commanding General of Training and Education Command, sums up his legacy best:
“Developing the mind as a weapon is a career-long process. Marines are continuous learners—they pursue mastery in the profession of arms, recognizing that the achievement of mastery is a journey, not a destination” (MCDP 7, 1-19).
MajGen Mullen understood that those in the profession of arms are on a journey with no destination. We can never be satisfied with our knowledge base. He read and learned continuously throughout his life and inspired others to do the same. Almost nine years ago, he showed me I was lacking in my own journey of developing my mind–and that has made all the difference.
Requiescat in pace.
Jeffrey E. Horn, Jr. is the Field Artillery Battalion S3 Trainer (“Fox 3”) at the Joint Readiness Training Center (JRTC). Most recently, he served as the Operations Officer and Fire Support Officer for the Field Artillery Squadron, 3d Cavalry Regiment, and he commanded twice in the 101st Airborne Division. He holds a Bachelor of Music from Southern Methodist University, a Master of Arts in Security Management from American Military University and a Master of Operational Studies from the Command and General Staff College.
