The paper reviews the mechanisms of hydrogen-related fracture, focusing on hydrogen-enhanced localized plasticity (HELP) and the effects of hydrogen on dislocation mobility. It discusses the role of hydrogen in increasing dislocation mobility under stress, leading to localized plastic deformation near the fracture surface. The authors present experimental evidence from high-resolution fractography and in situ TEM studies, showing that hydrogen can significantly enhance dislocation velocities, particularly at low temperatures and strain rates. They also explore the effects of hydrogen on macroscopic deformation, including the impact on flow stress and the occurrence of slip localization. The paper further delves into the theory of elastic shielding, where hydrogen atmospheres around dislocations reduce the repulsive forces between dislocations, leading to increased dislocation mobility. The authors conclude that while the mechanisms of hydrogen-related fracture are complex, the evidence for HELP and hydrogen-enhanced dislocation mobility is strong, supported by various experimental and theoretical approaches.The paper reviews the mechanisms of hydrogen-related fracture, focusing on hydrogen-enhanced localized plasticity (HELP) and the effects of hydrogen on dislocation mobility. It discusses the role of hydrogen in increasing dislocation mobility under stress, leading to localized plastic deformation near the fracture surface. The authors present experimental evidence from high-resolution fractography and in situ TEM studies, showing that hydrogen can significantly enhance dislocation velocities, particularly at low temperatures and strain rates. They also explore the effects of hydrogen on macroscopic deformation, including the impact on flow stress and the occurrence of slip localization. The paper further delves into the theory of elastic shielding, where hydrogen atmospheres around dislocations reduce the repulsive forces between dislocations, leading to increased dislocation mobility. The authors conclude that while the mechanisms of hydrogen-related fracture are complex, the evidence for HELP and hydrogen-enhanced dislocation mobility is strong, supported by various experimental and theoretical approaches.