Numerical simulations are used to examine long-rod penetration as a function of impact velocity. Similarities and differences between the penetration histories are analyzed, including penetration and tail velocities, penetration depths, crater radii, centerline interfaces pressures, and the extents of plastic flow in the projectile and target. The one-dimensional modified Bernoulli theory is often used to examine long-rod penetration into semi-infinite targets, and integral to the theory is a term that describes the resistance of the target to penetration. It is observed that the target resistance decreases with impact velocity, and it is shown that this is a consequence of both the residual phase of penetration and variations in the size of the plastic zone field. © 1993.