He was a German soldier stationed at a small bunker guarding a radio station close to a French town.
When John Miller's squad assaults the command post Steamboat Willie is seriously injured and, after burrying the 82nd Airborne Paratroopers he killed in the battle is set free un armed and blindfolded as he is ordered to walk 1000 paces north west to turn himself in to Allied patrols as a P.O.W. Instead he is most likely picked up by a Waffen SS patrol. In the final battle in Ramelle, Willie turns up among the Waffen SS assault and injures John Miller with a newly aquired rifle.
After the last Tiger tank was destroyed by P-51 Mustangs, Cpl Upham held Willie's group at gunpoint and when Steamboat Willie tried to reason with the corporal, Upham killed Steamboat Willie and avenged Private Mellish.