There were actually 3 drains on manpower: attrition, casualties, and new armies.
Between the wars, I built a large number of troops, so when I started the second war, I was nowhere near my maximum manpower. I think I only had 30,000 manpower in my manpower pool when the war started.
It's hard to estimate how many losses I suffered from attrition. To give you an idea, my armies spent most of the war in enemy territory. Considering their size, they ended up suffering 5% attrition (50 men per cohort) for every month for around 5 or 6 years.
Auxiliaries don't follow the same rules, so some of the armies I had in the field don't count for this.
Between the wars, I built a large number of troops, so when I started the second war, I was nowhere near my maximum manpower. I think I only had 30,000 manpower in my manpower pool when the war started.
It's hard to estimate how many losses I suffered from attrition. To give you an idea, my armies spent most of the war in enemy territory. Considering their size, they ended up suffering 5% attrition (50 men per cohort) for every month for around 5 or 6 years.
Auxiliaries don't follow the same rules, so some of the armies I had in the field don't count for this.