The term “Pentomic Era” in Army history refers to the five-sided pentagonal division organization, the Pentomic Division, which was in use from 1956 to 1962.
There are many lessons to be learned from the Pentomic Era, but Army officials rapidly realized the drawbacks of relying heavily on nuclear weapons, which has remained true ever since. The Army tested various nuclear war combat theories during Exercise Sage Brush in the fall of 1955. As a result of this test, the Army was obliged to reconsider its triangular infantry division structure, which had been in place since 1939. The Pentomic Division was unable to fulfill the stringent conditions needed to benefit from nuclear use. Pentomic Era provides a prism through which to view the survival and accomplishment of Ukrainian troops. The first, and most important, is that decision-makers who are considering the restricted use of nuclear weapons on the battlefield must also take into account the possibility of a full-scale nuclear conflict.