I've about finished reading "War by Numbers - Understanding Conventional Combat" by Christopher A. Lawrence, Potomac Books, University of Nebraska Press, 2017. Essentially the author, basing himself on the vast data bases compiled by Col. Trevor Dupuy on modern era wars (ca. 1600 to the present), attempts to prove the existence of constants which have maintained their validity through time and revolutionary technological progress. For example, attacker:defender ratios to achieve success have not changed in any significant degree. What struck me, though, was the author's comparative analysis of combat in urban and non-urban environment. Contrary to common belief, Lawrence claims that urban warfare is NOT more casualty-intensive either in human or material (AFV losses) terms. The only difference the author can tease out of the data (including urban battles such as Aachen and Hue) is that advances from successful attacks in built-up areas are between 1/2 and 1/3 of those on rural environments.
Anyway an interesting and compelling book especially for the developers of TOAW IV, TotH, Flashpoint Germany and lots of others. It would have been also useful for Battles from the Bulge.