text: Defense
  (including wire, abates trees,antitank ditches). Additionally, spider mine obstacle groups can be emplaced
  and grouped under one or several system operators with appropriate triggers and rehearsals.
  7-91. Commanderscan organize a perimeter defense to accomplish a specific mission,such as protecting a
  base or to provideimmediate self-protection,such as during resupply operations when all-around security is
  required. Duringa perimeter defense,leaders at all levels ensure that—
  (cid:122) Units physically tie into each other.
  (cid:122) Direct fire weapons use flanking fire to protect the perimeter.
  (cid:122) Field artillery and mortars are protected.
  (cid:122) Communications are secure and redundant systems in place.
  (cid:122) Obstacles are employed.
  (cid:122) Final protective fires are established.
  7-92. After committing the reserve, the commander must reconstitute the reserve to meet other possible
  threats. This reconstitution force normally comes from an unengaged unit in another portion of the perimeter.
  Perimeter Defense:Chip’yong Ni, Republic of Korea 1951
  During the Chinese Fourth Phase offensive, the 23d Infantry Regimental Combat Team,
  reinforced,used a perimeter defense to defeat elements of three People’s Republic of China
  armies,about 25,000 soldiers at Chip’yong Ni,Republic of Korea (seefigure 7-5on page
  7-22). From 13 to 14 February 1951,the 23d established a perimeter defense around the
  town of Chip’yong-Ni and blunted a major People’s Republic of China offensive. After a
  bitter fight,the Chinese forces withdrew at the cost of 51 United Nation’s Soldiers and an
  estimated 2000 Peoples Republic of China soldiers killed. The battle was a major defeat
  for the Chinese forces and led to subsequent United Nation offensives that forced the
  Chinese back into the North.
  Billy C. Mossman