text: Chapter 1
  underframe — The structure of a railcar under the deck that supports the weight of the load. (ATP 4-14)
  underground — A cellular covert element within unconventional warfare that is compartmentalized and
  conducts covert or clandestine activities in areas normally denied to the auxiliary and the guerrilla force. (ADP
  3-05)
  understanding — In the context of decision making, knowledge that has been synthesized and had judgment
  applied to comprehend the situation's inner relationships, enable decision making, and drive action. (ADP 6-0)
  unexploded explosive ordnance — (DOD) Explosive ordnance that has been primed, fused, armed or
  otherwise prepared for action, and that has been fired, dropped, launched, projected, or placed in such a
  manner as to constitute a hazard to operations, installations, personnel, or material and remains unexploded
  either by malfunction or design or for any other cause. (JP 3-42) Also called UXO.
  unified action — (DOD) The synchronization, coordination, and/or integration of the activities of governmental
  and nongovernmental entities with military operations to achieve unity of effort. (JP 1 Volume 1)
  unified action partners — Those military forces, governmental and nongovernmental organizations, and
  elements of the private sector with whom Army forces plan, coordinate, synchronize, and integrate during the
  conduct of operations. (ADP 3-0)
  Unified Command Plan — (DOD) The document, approved by the President, that sets forth basic guidance to
  all combatant commanders; establishes their missions, responsibilities, and force structure; delineates
  geographical areas of responsibility; and specifies functional responsibilities for designated combatant
  commanders. (JP 1 Volume 2) Also called UCP.
  unified land operations — The simultaneous execution of offense, defense, stability, and defense support of
  civil authorities across multiple domains to shape operational environments, prevent conflict, prevail in large-
  scale ground combat, and consolidate gains as part of unified action. (ADP 3-0)
  unit — (DOD) 1. Any military element whose structure is prescribed by competent authority. (JP 3-33)
  unit distribution — A method of distributing supplies by which the receiving unit is issued supplies in its own
  area, with transportation furnished by the issuing agency. (FM 4-40)
  unit historical officer — An individual, military or civilian, who is designated as the unit historian and is
  responsible for military history activities. (ATP 1-20)
  unit history — An informal narrative that covers the entire history of a specific unit, written in an easy-to-read
  manner for the benefit of the Soldiers. (ATP 1-20)
  unit line number — (DOD) A seven-character alphanumeric code that describes a unique increment of a unit
  deployment, i.e., advance party, main body, equipment by sea and air, reception team, or trail party, in the
  time-phased force and deployment data. (JP 3-35) Also called ULN.
  unit movement data — (DOD) A unit equipment and/or supply listing containing corresponding transportability
  data. (JP 3-35) Also called UMD.
  unit recovery team — Non-mortuary affairs personnel available to conduct immediate recovery operations.
  (ATP 4-46)
  unity of command — (DOD) The operation of all forces under a single responsible commander who has the
  requisite authority to direct and employ those forces in pursuit of a common purpose. (JP 3-0)
  unity of effort — (DOD) Coordination and cooperation toward common objectives, even if the participants are
  not necessarily part of the same command or organization that is the product of successful unified action. (JP
  1 Volume 2)
  Universal Time — (DOD) A measure of time that conforms, within a close approximation, to the mean diurnal
  rotation of the Earth and serves as the basis of civil timekeeping. (JP 5-0) Also called ZULU time.
  unmanned aircraft — (DOD) An aircraft that does not carry a human operator and is capable of flight with or
  without human remote control. (JP 3-30) Also called UA.
  unmanned aircraft system — (DOD) That system whose components include the necessary equipment,
  network, and personnel to control an unmanned aircraft. (JP 3-30) Also called UAS.
  unobserved fire — Projectile points of impact or burst not observed. (FM 3-09)
  unprivileged belligerent — A person who, by engaging in hostilities, has incurred the corresponding liabilities of
  combatant status (for example, being subject to attack or detention), but who is not entitled to the distinct
  privileges of combatant status (for example, combatant immunity and prisoner of war status upon capture).
  (FM 6-27)
  urban operations — Operations across the range of military operations planned and conducted on, or against
  objectives on a topographical complex and its adjacent natural terrain, where man-made construction or the
  density of population are the dominant features. (ATP 3-06)