8 July 2025 – We are deeply saddened by the passing of Dr. J. Mark Pullen, Director Emeritus of Mason’s C5I Center. Dr. Pullen served as Director of the C5I Center from 2005 until his retirement in 2020 and was also a beloved Professor of Computer Science at George Mason. Under his leadership, Mark maintained the Center in its growth and recognition as a leading institution for national and global research in C5I. Mark was also recognized as a pioneer in distance education, personally developing open-source synchronous Internet software to deliver online MS degree programs in Computer Science long before online learning became ubiquitous. This work demonstrated his forward-thinking approach and commitment to making high-quality education accessible to the right students “in the right place at the right time.”
Mark’s contributions are highlighted by his strong academic expertise, practical engineering skills, and internationally recognized operational and strategic insights. He skillfully balanced developing the nation’s security future workforce, teaching leading-edge courses in computer networking and networked virtual environments with knowledge and strong mentorship, while simultaneously leading developmental solutions for complex defense and cybersecurity problems.
His direct contributions significantly enhanced interoperability of command-and-control systems through leading edge modeling and simulation, personally leading such efforts as the “Extensible Modeling and Simulation Framework” (XMSF) and the “Command and Control – Simulation Interoperation” (C2SIM) initiatives, significantly influencing NATO and SISO standards still used worldwide. After retiring from Mason, Mark continued to “pay it forward” to the future of our nation’s security, as he was personally recruited to participate in advancing interoperability standards through his efforts working with NATO’s “Coalition Warrior Interoperability eXploration, eXperimentation, eXamination, eXercise” (CWIX) events.
Beyond his recognized technical expertise, Mark was a dedicated teacher, respected mentor, and valued colleague. His sustained commitment to problem-solving and supporting students and peers alike helped create the collaborative environment the C5I Center still benefits from today. Dr. J. Mark Pullen, Director Emeritus, will be greatly missed, and his impact will continue through the focused efforts he started, the standards he helped develop, and the many people he guided throughout his career.
The tribute and obituary from Mark’s family is available here.
