A thermodynamically-consistent viscoplastic damage model was used to elucidate dynamic
compressive response of an HCP material beryllium. Twins accommodate plastic deformation, which is otherwise limited by the contribution from dislocation slip in HCP metals. An isotropic model for deformation twinning adapted in this work is computationally efficient, yet physically-based. The model implements contribution to plasticity from twinning using physically-based kinetics of twinning. Dislocation substructure evolution was used to inform a nucleation criterion for a microcrack. Under global compression, the sliding of a primary microcrack induces formation of a secondary microcrack, commonly known as a wing-crack. Effective elastic compliance considers softening due to a distribution of spatially evolving microcracks. Internal variables were constrained based on the laws of thermodynamics. Calibrated material constants were used to demonstrate the applicability of the model to simulate failure under a range of strain rates that are characteristic of Hopkinson bar experiments.