fj44 said:
Friedrich Wilhelm of Prussia started it, not Napoleon. Just a minor historical footnote.
There were guards units long before Friedrich Wilhelm, he was just famous for being obsessive about his guards (including recruiting by any means necessary especially tall men, so that they were sometimes referred to as the "Potsdam Giants").
In the British Army for instance the Coldstream Guards go back to 1650, and many other armies had guards units before this.
The origin of the term is in guard units for the sovereign (eg Praetorian Guard in Rome or Varangian Guard in later Byzantine times), but it became a term for elite units, which were then used for key attacks, etc.
Napoleon used his Imperial Guard units as a combined group, which was unusual (before and after). He also had an usually high proportion of his French troops in the Guards (though he usually had many other allied troops as well).
In Victoria:
a) there is no combined arms effect
b) there is no soft/hard split, all unit are soft in HOI terms
c) there is no stacking penalty for land units (though there is a penalty for ships, which limits effective fleet size to about 30 ships)
d) the defence is greatly enhanced over the course of the game - entrenchment levels can reach as high as 140% (high army tech, plus engineers) plus fort levels and terrain bonuses. Attacking such highly entrenched troops is extremely difficult [Think WW1 trench warfare]
e) the time scale is longer, so the strength of the economy and its ability to support the troops is more important - maintenance cost includes supply requirement in HOI terms.
f) units are linked to the underlying soldier populations which provide their men - losses in the unit are reflected in the population
g) you can increase available manpower rapidly by converting pops into soldiers (though subject to limitations depending on government policy in V:R, eg pacifist can't do this, you need full citizenship policies to convert non-national pops, etc)
h) ability of troops change very significantly between 1836 and 1935 as more advanced techs are developed - these flow directly to existing troops without need to overt upgrading
i) brigades are included when units are created (only) - like HOI1 not HoI2/DD
Army design depends on circumstances - especially available manpower and budget. Native quality troops are extremely cost effective in terms of fighting ability per maintenance cost (1/10 maintenance cost of regulars), though they have the same establishment cost and have lower reliability and higher attrition losses.
I typically would only include artillery or tank brigaded divisions in armies with high proportion of that arm - they slow down the whole army a lot. You do want tanks if you really have to attack a well entrenched enemy though.