I suppose the biggest difference between Iraq/Afganistan and WWII/Vietnam is the intensity of the conflicts, the recent conflicts have been low level wars with periods of high intensity with a steady but small numbers of casualties where as the older conflicts were more meat grinders which depleted the prime generations of the time and there was a very obvious casualty problem, combined UK and US casualties are in the 2000 region for Afghanistan (about 2500 or so for the overall coalition casualties) a couple of battles in WWII or Vietnam would far exceed these.