the combined arms team that enhances mobility of the force by projecting elements across an obstacle, wet ordry, in support of assured mobility. It is also applicable to joint, interagency, or multinational forces and isspecifically written as a dual manual between the United States (U.S.) Army and the U.S. Marine Corps(USMC). Although other branches contribute to gap-crossing operations and are included in the discussions,this manual focuses on the engineer contribution to gap-crossing operations, while acknowledging thesignificant role of other branches and capabilities. This manual follows the principles and tenets found in FieldManual (FM) 3-90, FM 3-34, and FM 3-34.2 that continues the discussion of mobility and gap-crossingoperations. It recognizes the contribution of the entire combined arms team to gap-crossing operations and themulti-Service capabilities that exist to support gap-crossing operations at both the tactical and operationallevels. Finally, it addresses the specifics associated with gap crossing in support of combat maneuver and lineof communications (LOC) gap crossing, integrating the considerations created by the significant changes todoctrine and force structure that have occurred since FM 90-13 was published in 1998.This FM is the tactical commander's and engineer staff planner's manual and primary resource forunderstanding gap-crossing operations. This manual follows the mobility concepts and fundamentals outlinedin FM 3-34.2 and is intended for use by commanders and their staff at both the operational and tactical levels. Itrelates the engineer-focused aspects of gap crossing to the functional area of combined arms mobilityoperations, incorporating new concepts associated with the expansion of the existing Army task (ART)Conduct Gap-Crossing Operations and the advent of the modular force structure.