The classic book on the subject is Healy's "Ancient Assyrians".

Simply, the Assyrians innovate in Meopotamia through:

• Creating a standing army by requiring male military service, instead of using peasant levies.

• Perfecting the chariot, which to answer the follow-up question, absolutely wrought havoc among the foot armies prevalent up until that time.

• Locking upon expansion as a central method of cultural growth: it's strange to think of this idea having to be invented, but warfare had previously been about local border disputes, whereas the Assyrians after Sargon establish firm military borders of their own while deliberately striking deep into the heart of enemy territory.

What was warfare like? Imagine a rabble of professional farmers, maybe a few tens of thousands, handed weapons and gathered in a loose mob.

Assyrians invented shock and awe. No matter how fanciful the ancient numbers, we may assume they brought armies of perhaps 100,000, maybe more to battles, and came roaring across the alluvial plains and flatlands of Mesopotamia in brutal frontal assaults. Heavy chariots smashed infantry divisions apart, Chariot-borne archers and cavalry archers stormed the enemy with arrows, and it was frequently an utter rout as the essentially Neolithic armies of their enemies disintegrated under this new kind of assault.

Ill follow up that question with: what kind of weaponry and armor would their armies use?

If I could ask a follow up, what was Assyrian warfare like during the Neo-Assyrian period?

I have found an absolute fascination with the Assyrian equipment, coud I ask if the iron helmets and lamellar/scale I keep seeing in artistic reconstructions are based off actual finds or on fresco's/images only?