oh, should be known to the devs...
first, there is the problem with the pre-determined level of aggressiveness in quite a few theaters of war.
it also leads to problems in the Russian-Japanese scenario, in the GC 1850 whilst besieging cities, or for instance, Sioux taking over Chicago...
second, its a, i claim so unless they tell me better, still not identified problem within the calculation of combat results / sieges which is giving you this problem of extreme magnitudes like zero losses vs. all destroyed/captured. and thus the broken moral
Kensai is right, 1.02 did some good, but did not solve the basic problems.
For modding this kind of problems, McNaughtons work is a pretty important strong foundation for re-balancing it further more with regard to new units stats either

...not paid by AGEOD.
however, prone to throw them into disarray.
PS:
‘Everything is very simple in War, but the simplest thing is difficult. These difficulties accumulate and produce a friction which no man can imagine exactly who has not seen War . . . in War, through the influence of an infinity of petty circumstances, which cannot properly be described on paper, things disappoint us, and we fall short of the mark.‘
Clausewitz