Marine Maxims is a collection of fifty principle-based leadership lessons that Thomas J. Gordon acquired commanding Marines over a career spanning three decades of service. Dealing with the complexities and challenges of the contemporary operating environment requires an internal moral compass fixed true. These maxims focus on developing inner citadels of character, moral courage, and the resilience to persevere in a contested domain where information is key. Its purpose is to provide future leaders with a professional development plan that will steel their resolve and enable them to lead with honor. Thematically, these maxims build upon a foundation of character, courage, and will. To be effective, a leader must model and inspire the will to persevere in the face of danger or adversity. The essence of effective leadership is credibility. A leader's credibility is derived from a congruence of competence and character. Exceptional leaders are not remembered for what they accomplished, but how they did it. Those that lead with integrity will be remembered as a leader worth following.