My research investigates the interplay between plasticity-based phenomena, hydrogen, and mechanical behavior in high-HE-resistant steels using advanced electron microscopy techniques (ECCI, EBSD, 3D EBSD, TEM). I use microstructure-based approaches to quantify how hydrogen content affects deformation variables (dislocations and twins) associated with strain localization, strain hardening, and damage. The approach explores the effect of hydrogen on plasticity-based mechanisms determined by statistical microstructural parameters, such as strain hardening, and microstructural parameters informed by local deformation conditions, such as twin/slip nucleation, strain localization phenomena, and damage. The analysis aims to explore the impact of hydrogen-dislocation interaction effects on large-range plasticity effects, providing further insights into the impact of hydrogen on relevant aspects of plasticity, such as spatial distribution (strain localization phenomena), strain accommodation, strength, and damage. The outcome of this research is implemented in dislocation-based models of strain hardening and damage that provide a more comprehensive view of hydrogen-induced plasticity phenomena in high-HE-resistant steels.