Researching the history of my fathers infantry battalion I am struck by the rate of attrition. In the 11 months between D Day and VE day his battalion lost 4 COs Killed or wounded and had a total of over 900 KIA, wounded or MIA in the first 3 months, 500 in the first month alone, well over 100% casualties. Presumably this battalion was not unique. Where did all the replacements come from? I understand it may be possible to train a fit young man to take his place in a rifle company or drive a tank in a few weeks or months; but how long does it take to train a battalion CO, other officers and senior NCOs? Given the relatively small size of the prewar army where did they all come from? Also how did they maintain unit cohesion over time? Battalions would have trained as units for 2 years and would have landed as tight knit efficient units which within days would have changed to a group of virtual strangers. How did this change units fighting effectiveness?