Book excerpt: Military Leadership in the 21st Centuryaims to provide junior commanders or entry-level military officers with an introductory-level appreciation of the key concepts and issues related to military leadership from a social-behavioral science perspective. The book focuses on "direct-level" or "team leadership". It has three main themes: (1) the human dimension of military operations and organization; (2) the main approaches to direct or team-level leadership, including the trait-approach, values or ethical leadership, and leadership styles and behaviors; and (3) the challenges of leadership in 21st century military operations, organizations, and, the 21st century military profession. Besides learning key leadership-related concepts and issues, readers are also introduced to key events, institutions and social-behavioral scientific research programs that have shaped contemporary military leadership doctrines and systems.