For analyzing the damage propagation in glass, a detailed understanding of the occurring physical mechanisms leading to damages is crucial. During the penetration of a long, slender heavy-metal rod into borosilicate glass, X-ray images help to identify how deep the rod has advanced into the glass cylinder at different points of time. In case of brittle material, a damage front runs ahead of the penetrating rod. By means of high-speed cameras, the propagation of this damage front can be observed. The simultaneous use of optical and X-ray observation techniques allows to analyze the velocity of the precursory damage front depending on the penetration velocity. For solving this problem, the roles of projectile and target have been reversed, that is, in the “reverse ballistic impact test”, the target (in the picture series, the glass body to the left) is shot at a stationary projectile (in the picture series, the slender rod to the right). The analysis of such recordings supports the modeling of failure behavior of the brittle material.