Marine Corps Doctrinal Publication (MCDP) 3, Expeditionary Operations, establishes doctrine for the conduct of military operations by the U.S. Marine Corps. It describes the Marine Corps as an expeditionary force-in-readiness that is manned, trained, and equipped specifically to respond quickly to a broad variety of crises and conflicts across the full range of military operations anywhere in the world. It emphasizes the naval character of Marine Corps forces. This naval expeditionary character provides capabilities both to forward deploy forces near the scene of potential crises as well as to deploy sustainable, combined arms teams rapidly by sea and air. With reduced overseas presence in terms of force levels and bases, these capabilities have become essential elements of our national military strategy. This publication also underscores the value of Marine Corps forces as a highly cost effective option in a wide range of situations, including crises requiring forcible entry. Importantly, this publication establishes versatility and adaptability as critical capabilities in a broad range of circumstances for expeditionary forces in an uncertain world. Finally, this publication describes the Marine Corps' key expeditionary concepts.