Some maths could help:
- x is your bronze army supply.
- Highest power per 1 unit for Human is Swordmen.
Equation: (x * 83) + (x/3 * 248) = 1,000,000 power.
=> x = 6024
If you bronze power reach 6000, your human bronze and silver army power will be 1 mil. I think other races could be similar. And you easily make 11+ gold troops.