The S4 is the principal staff officer for coordinating the logistics integration of supply, maintenance, transportation, and services for the command. The S4 is the link between the support unit and his commander plus the rest of the staff. The S4 assists the support unit commander in maintaining logistics visibility with the commander and the rest of the staff. The S4 must also maintain close and continuous coordination with the S3. At the battalion level, the S4 not only coordinates activities but also executes requirements for the commander and unit. (FM3-09.21, 1-14; FM 100-5, 4-14)