The Army has undergone a dramatic transformation over the last five years. It has become a modular "brigade-based" Army that is more responsive to combatant commander's needs. It better employs joint capabilities, facilitates force packaging and rapid deployment, and fights as self-contained units in non-linear, non-contiguous operations. Evolving from a rigid, multiecheloned formation to a more flexible, centralized structure that eliminates redundancy and streamlines support by removing unnecessary layers while remaining responsive to the needs of a joint and expeditionary Army. This publication provides fundamental guidance for the employment of the theater sustainment command (TSC) and expeditionary sustainment command (ESC) to command and control Army deployment and sustainment operations conducted in support of joint and multinational operations across the spectrum of conflict. Field Manual (FM) 4-94, "Theater Sustainment Command," establishes Army doctrine for operational-level deployment and sustainment by providing overarching doctrinal direction for Army operations conducted in support of full spectrum operations detailed in other Army manuals. This edition of FM 4-94, the first revision since 2003, describes the TSC and how it relates to the combatant command as part of the modular Army. This manual will fill an immediate need, providing commanders and their staff with the doctrinal tools to succeed. In its current form, this manual provides the intellectual underpinnings that lie at the core of how a TSC and its subordinates operate. It gives an understanding of the modular logistics structure and how to apply effective command and control. By reading this FM, commanders and their staffs will be familiar with the TSC mission, organization, roles and key tasks to perform.