 The tank scene was created completely using CGI . The only actual footage from the scene was the background . A computer @-@ generated tank , along with women , were designed on a computer . Then , special effects shots of smoke and explosions were layered on top of the vehicle to give it a more life @-@ like appearance . Bruce Harwood , who portrayed Byers , noted that the action sequences in the episode were a challenge . He explained , " It 's pretty difficult on a set when the stuntmen come up to you and go , ' Don 't worry , you 'll be safe , Nothing to worry about . Okay . Everyone put their safety glasses on . ' " 
