Rolling-direction tensile specimens of 0.31 C quenched and tempered alloy plate steel displayed cup-and-cone, split-layered, neck-and-split, and square-break fracture configurations over distinct temperature ranges as testing temperature was lowered from 300 to −320 F. Formation of the neck-and-split configuration was investigated in terms of stress state, temperature, void formation, and anisotropy. Electron fractography identified quasicleavage as the fracture mode of the initially occurring longitudinal split. The brittle fracture phenomenon resulting in the neck-and-split fracture of plate specimens occurs under a unique combination of conditions.