You make a good reference in the reminder about variation over time. I am finding that distances mentioned by commentators in the Peninsula are also a confusion, both over time and between employment of different national practices. British chroniclers frequently mention distances in terms of "leagues"--but usually without mentioning WHOSE league they are talking about! A variety of British memoir-writers use "league" to mean an equivalent to 3 English miles, some relate it to about 4 English miles, many never mention which scale they are using, and I wouldn't be surprised if for a number of them that which scale of league they are referring to CHANGES over time to fit majority practice! Of course, there is a French league (and some variety there, if I recall correctly), and several different leagues in use in Spain. It must have been hellacious trying to get a common reference for measurement just within the same army, let alone making assessments in reference to another of the belligerents.
We've seen similar debates here regarding weight with respect to the relative natures of artillery in different national services. Again, the length of a French pace, nominally two feet, is two French feet, and thus about 25.3 English inches (if I calculate aright). It would be interesting project to set up a matrix of known distance and weight measures for comparison and reference...the sort of exercise that could really benefit from the wealth of diverse knowledge possessed by Forum members ;^}
Happy holidays - Howie