The dynamic structure a magnetic domain wall in a thin film with large uniaxial anisotropy perpendicular to the plane of the material has been determined by numerical integration of the Landau-Lifshitz-Gilbert equation. The geometry corresponds to a domain wall whose structure is uniform along the wall, but can vary normal to the wall and normal to the plane of the material. For external fields in the range of a few Oersted, a constant mobility is observed. In this region, the wall remains flat and horizontal Bloch lines (HBL) are not formed. At larger fields, HBL's are formed that propagate through the wall and punch through at the opposite surface from which they formed. During punch through, the region of the wall undergoing a quick 180-degrees rotation is seen to move backward compared with the rest of the wall. This causes the average wall position to be stationary during punch through. At larger fields, the structure of the domain wall is significantly more complex and multiple HBL's are found in the domain wall.
