Armies of mixed units

I get that it is good to have a mix of attacking and defensive units, but are there any other advantages?

I mean in the ancient world, does having infantry type units increase the effectiveness of archers? In normal war they need infantry in front of them to protect them, does this translate in the game?

To answer your question. No having certain mix of units wont buff another type of unit. However, having a bunch of cheapie units to inflate your stack size will get you better rolls due to stack bonuses. This works well when you have units with high att or def backed up by a ton of cheap units to inflate stack size.

Imperialist is a strategy that shows how mixing units and abusing stack bonus can be very powerful.

Out numbering cities or armies with large amount of infantry and a considerable amount of main attack units thrown in is very powerful. The stack bonus due to the size of your army overall buffs your main attack rolls reducing the units you lose.

For example.
50 imp infantry attacking 20 defending infantry will win everytime. But you will lose around 25-35 infantry in the battle.

However 40 infanty with 10 tanks thrown in versus 20 infantry. You will only lose about 15-20 units due to abusing stack bonus.

Having 100 infantry 10 tanks attack a city with 8 infantry units is significantly better than just having 10 tanks attack it solo. Sure both cases will win, but you will lose a lot less with he inflated stack size.

Dont quote me on any of the figures because I might be wrong with my estimates.