The drag force acting on a kink moving rigidly and uniformly along the dislocation line and in the atmosphere of mobile octahedral (heavy) interstitials is investigated numerically in anisotropic body‐centered‐cubic metals. It is shown by extensive computer modeling experiments that the drag force versus normalized kink velocity plot goes through a maximum which is composed of three subpeaks, one acoustic and two optical in character. The acoustic part and the optical mode‐2 are strongly and selectively associated with the isotropic and the pure shear parts of the elastic dipole tensor of the interstitial species, respectively. An extremely accurate and the concise analytical expression is deduced for the linear viscosity regime which exhibits the behavior of Navier–Stokes fluids, which can be used directly in Snoek–Ko¨ster relaxation. The flow stress theory of Seeger for the ultrahigh‐purity body‐centered‐cubic metals is extended and coupled with the present treatment of the kink dragging which yields an excellent agreement with the dynamical strain aging experiments in Fe‐C and Fe‐N alloys.