We explore the impact fragmentation of armor-grade boron carbide cylindrical targets using spherical tungsten carbide projectiles at impact velocities spanning from 100 to 550 m/s. In situ radiography of the target captures the target’s failure history under ballistic loading, while postmortem X-ray-computed tomography scans characterize the generated fracture surfaces in detail. The combination of the two techniques reveals several impact stress-dependent regimes of fragmentation, moving from minor or no fragmentation with projectile defeat in a dwell process up to macro-cracking that extends through the target as striking velocity increases. Our in situ radiography initially suggests the depth of penetration increases linearly with impact velocity, with a zone of comminuted material formed by intersecting micro-cracks directly below the projectile-target interface, terminating at a macro-crack-generated fracture conoid. However, postmortem X-ray-computed tomography shows that the depth of penetration actually depends on impact stress, though the observed macro-crack features remain largely the same between the two diagnostics. At the highest velocities, radial cracks along the striking surface of the boron carbide cylinders penetrate through the fracture conoid to the rear surface of the cylinders. Analytical and finite element models of these ballistic impacts confirm the stress dependence of fracture conoid generation and penetration of radial cracks.