Short (I hope!) comparison between Speculative Fiction
Space Navies and Armies

First, I would re-iterate my theory that the Navy ranks used
in 'Star Wars' basically reflect the in-theatre operations
of a particular sector. The reason this is is due to the apparent
low positions of the rank of 'Captain', which is more comparable
to said rank in Terran Armies (i.e below Major and above Lieutenant),
in the 'Star Wars' universe.

But this whole confusion described in previous posts misses the
point suggested in the actual movies, which is explicitly referred
to by Tarkin, which is that the 'fear of force, not force itself',
is all that is required to police the Galaxy. It is only sources
connected with the Expanded Universe which indicate a much
larger Imperial Army.*

This discrepancy could have two points/explanations: The
Imperial Army could refer to the COMPNOR organisation [or
its (presuming it has one) paramilitary wing]: the ideological
and propaganda (in short) wing of the Empire (COMmission for
the Preservation of the New ORder);

Or it could simply reflect a commonality in "soft" SF.
All space Navies in other fictional 'verses tend all to be of
comparable size**, regardless of the apparent population of
each society described, but they all seemingly have an infinite
capacity (in terms of either technology, manpower or both) to
construct starships and other materiel.

The 'Starfleet' of the UFP of "Star Trek" is a good example of this:
a body which has a fairly small fleet compared to its population,
but much smaller than the Imperial Fleet in "Star Wars", and yet
a very high productive capacity for constructing starships.
Even higher than either the Galactic Empire or even the
'Culture'. Maybe that's what they do with all the unemployed
people?

Saying that, I think "Star Wars" does put this military
trope on its head: 'Starfleet' is a very large military
body for a supposedly non-militaristic society and the
apparent manpower of the Galactic Empire is probably
reasonable considering a) its vast population, easily
a million times that of the UFP's Human population
and b) THEY USE DROIDS ffs! unlike in 'Star Trek'
( and no factory ships or GSVs in "Star Trek" unlike
the 'Culture' novels). Anyway, my COMPNOR theory
probably makes sense: most discrepancies in the 'Expanded
Universe' can be more or less explained.

Of course, this is another excuse for me to have a go
at "Star Trek" but hey the evidence is there.

*Of course all we see in the actual movies are Clone-
and Storm Trooper units but, supposedly,
the Stormtrooper corps is a separate entity from both the
Imp Army and Navy (perhaps 'Navy' and 'Army' refers to two
Officer corps, either of which has direct authority over
non-commissioned troops/crews)

**The 'Earth Alliance' (Babylon 5, Human population is explicitly
less than 10 billion) has about 8000 warships and thousands of
support vessels and tenders/troop carriers, 'Starfleet' has
probably 20K starships and 40K science vessels [plus thousands
of transports, shuttles, unmanned drone transports etc] while
the Galactic Empire has (quoting Han Solo) 2000+ Destroyer-class
vessels, albeit thousands more cruisers, tenders
and shuttles and a population in the thousands of trillions.