High-strength low alloy steels (HSLA) have been designed to replace high-yield (HY) strength steels in naval applications involving impact loading as the latter, which contain more carbon, require complicated welding processes. The critical role of HSLA-100 steel requires achieving an accurate understanding of its behavior under dynamic loading. Accordingly, in this paper, we experimentally investigate its behavior, establish a model for its constitutive response at high-strain rates, and discuss its dynamic failure mode. The large strain and high-strain-rate mechanical constitutive behavior of high strength low alloy steel HSLA-100 is experimentally characterized over a wide range of strain rates, ranging from 10−3 s−1 to 104 s−1 . The ability of HSLA-100 steel to store energy of cold work in adiabatic conditions is assessed through the direct measurement of the fraction of plastic energy converted into heat. The susceptibility of HSLA-100 steel to failure due to the formation and development of adiabatic shear bands (ASB) is investigated from two perspectives, the well-accepted failure strain criterion and the newly suggested plastic energy criterion . Our experimental results show that HSLA-100 steel has apparent strain rate sensitivity at rates exceeding 3000 s−1 and has minimal ability to store energy of cold work at high deformation rate. In addition, both strain based and energy based failure criteria are effective in describing the propensity of HSLA-100 steel to dynamic failure (adiabatic shear band). Finally, we use the experimental results to determine constants for a Johnson-Cook model describing the constitutive response of HSLA-100. The implementation of this model in a commercial finite element code gives predictions capturing properly the observed experimental behavior. High-strain rate, thermomechanical processes, constitutive behavior, failure, finite elements, Kolsky bar, HSLA-100.