The Pentomic Concept and the Combat Arms Regimental System
The armistice in Korea did not bring about the rapid demobilization of infantry units that traditionally followed the cessation of hostilities in American military history. President Dwight D. Eisenhower gave the reason for this departure from the usual pattern when he said: "We have won an armistice on a single battleground-not peace in the world. We may not now relax our guard nor cease our quest." There was, nevertheless, a gradual reduction of both personnel and units throughout the mid-1950's. When the Korean armistice was signed, the active Army had ninety infantry regiments, a year later the total was seventy-four, and by the end of 1956 only fifty-four regiments were active. The number of separate infantry battalions decreased from thirty-one to twenty-six during the same period, while the infantry's personnel strength dropped from 251,685 to 133,931.
By December 1954, all National Guard infantry units that had been federalized during the Korean War reverted to state control and were reorganized at their home stations. Several Regular Army infantry regiments were activated to replace them in the active Army. The number of these organizations, however, never equaled the total of National Guard units released, and some of the Regular regiments were inactivated as the authorized strength of the Army declined. Although the number of units decreased, the responsibilities of the infantry remained worldwide. In December 1956, in addition to those in the continental United States, infantry units were stationed in the Canal Zone, Alaska, Hawaii, Iceland, Italy, Berlin, West Germany, Japan, and Korea. In Korea, two infantry divisions with three organic infantry regiments each were still on duty.
The period immediately following the Korean War was a difficult time for the infantry. The new administration re-evaluated the national military policy, and with this "New Look" the United States entered the so-called "Era of Massive Retaliation." The doctrine of massive retaliation rested on the assumption that the threat of instant and large-scale nuclear reprisals would serve as an effective deterrent to future wars and, therefore, make large conventional forces unnecessary. It emphasized the role of the Air Force in national defense and relegated the Army with its infantry to an inferior position.
Unable to convince the administration of the likelihood of small limited wars in the future and of the need for what he called "a strategy of flexible response," General Maxwell D. Taylor (then Army Chief of Staff) decided that it was necessary to reorganize and modernize the Army to make it readily adaptable to the requirements of the atomic battlefield. As a result, starting in late 1956 Army units were reorganized under the Pentomic system. Two of the most salient characteristics of this concept were reflected in its name-pentagonal structure and atomic capability. Low-yield tactical nuclear weapons became a mainstay of the Army, and an organization based on five major subordinate units replaced the traditional three basic elements of the triangular system.
Many features of the Pentomic organization were dictated by the nature of atomic warfare as well as by a desire to take full advantage of the tremendous technological advances of recent years. For example, the absolute requirement for wide dispersion on the nuclear battlefield to avoid offering the enemy any single lucrative target was an important consideration in adopting an organization with five small basic combat units, while new developments in the field of communications made a broader span of control possible. Since the Soviet Union had acquired an atomic capability in 1949 and from all indications its nuclear arsenal had kept on growing steadily, an enemy with atomic combat power was not entirely theoretical. In order to be successful in a nuclear war, U.S. infantry units had to be small and lean, more powerful and harder hitting, self-sufficient, and geared for long periods of independent action on a wide and fluid battlefield. They had to be capable of rapid and effective concentration in the attack as well as equally rapid dispersal for defense. The Pentomic system attempted to give the infantry all of these capabilities.