( ~ 11:00 )

Armies need to have an efficient supply system in order to survive. Not only for food and stuff, but also medical kits, materials to fix machinery when it breaks down, ammunition, etc.

These are also fantastic ways to add strategic elements to warfare. Taking over enemy supply lines or points can hurt them tremendously while giving yourself a great edge.

( ~8:50 )

Defense in depth over static defense usually. They both have value, but it depends on usecase.

( ~ 7:30 )

In any world where technology on the level of atomic weaponry exists (nuclear bombs), there must either be a reason for why they are not used (such as in Dune), or they should just be used.

A reason could be through universally recognized and obeyed law, or that counters against such weaponry exist, making them useless.

( ~3:55 )

In futuristic scenarios, armies marching together closely (i.e. massing) is dumb because this makes them an easy target for area damage focused weaponry such as artillery, tanks, etc.

Better to have more spread out formations.

That is, if no technology or magic exists to counter such vehicles, such as mobile shield generators, then it does make sense to walk in a tight formation as centralized command is easier.

( ~2:50)

The larger the size of an army, the more autonomy lower-ranking officials need. A centralized command becomes much more difficult when the area over which to fight is enormous.

Futuristic Armies are in need of efficiency, needing clerks, communication networks, etc. To keep themselves supplied and directed.

( ~2:10)