4-42. Army forces arrive via the most efficient use of available lift, and speed is usually a critical factor during DSCA operations. Based on mission and mission, enemy, terrain and weather, troops and support available, time available, and civil considerations (METT-TC), the theater army may be required to establish reception, staging, onward movement, and integration operations. The theater army normally assigns reception, staging, onward movement, and integration to the theater sustainment command (Army) and its attached expeditionary sustainment command (ESC). Upon arrival in the AOR, attachment of the unit transfers from the force provider (United States Army Forces Command or the National Guard Bureau) to the theater army. The theater army passes tactical control of the unit to the ESC or other Army headquarters responsible for reception, staging, onward movement, and integration. Upon arrival of the deploying unit's chain of command, the theater army and gaining operational commander establish a relationship of direct liaison authorized in order to facilitate communications and planning. The ESC receives personnel and equipment at the joint theater base established in or near the joint operations area (reception). When the unit is fully assembled, it moves as a unit to a designated assembly area within the joint operations area (staging). For DSCA, the joint theater base may be a BSI, but the arriving forces could also self-deploy and move directly to their designated areas of operation, bypassing a staging area, and establishing logistics support from the ESC and designated BSI from there.