Knowledge elicitation (KE) plays a key role in the design and development of human-centered military systems. KE is critical for identifying the information necessary for effective system development, including defining the basic system functionality, user interface design, and human-machine function allocation. Military environments pose special challenges to the KE process, due to the complexity and amount of knowledge being elicited, the difficulty of accessing experts, and difficulty of conducting KE in an ecologically-valid manner. In this paper we discuss the theoretical and practical aspects of KE in complex military environment, and outline the available KE techniques and recent computerized KE tools. The paper concludes with a 'lessons learned' summary regarding knowledge elicitation in military settings.