The response of turbulent enstrophy to a sudden implementation of spanwise wall oscillation (SWO) is studied in a turbulent channel flow via direct numerical simulation. In the beginning of the application of SWO, a significant correlation is formed between omega (y) (') and omega (z) (') . A transient growth of turbulent enstrophy occurs, which directly enhances turbulent dissipation and drifts the turbulent flow towards a new lower-drag condition. Afterwards, the terms related to the stretching of vorticity (omega (x) , omega (y) (') , and omega (z) ), the inclination of omega (y) (') by , the turn of omega I" (z) by , and the horizontal shear of omega I" (z) by are suppressed due to the presence of SWO, leading to attenuation of the turbulent enstrophy.