For the sake of completeness:
http://www.eu4wiki.com/Army#Composition
As has already been posted, in most circumstances the ideal combat stack is:
(1) Two to six cavalry units, not exceeding your cavalry support limit;
(2) Enough infantry to fill your combat width;
(3) A full combat width of artillery; and
(4) Reserve infantry up to the supply limit to fill out casualties.
The double cost of cavalry makes cavalry-heavy armies inefficient in most circumstances. Cavalry is usually superior to infantry when the new cavalry units show up due to increasing military tech level, but it will then become outclassed by newer infantry units. If you have the income to support lots of cavalry, then the calculus naturally changes.
Artillery should never see combat casualties and massively boosts your combat and siege effectiveness. The limit for artillery is not manpower but income, and it's all too easy to go bankrupt trying to support a huge artillery train in the early game. Your combat width depends on terrain, so as has been said above, it's perfectly possible to economize on artillery. I usually try for full combat width because I cannot always guarantee an engagement in low-width defensive terrain and prefer to not lose engagements due to insufficient artillery support.
The exception to the cavalry rule is hordes and some Eastern-tech countries like Poland. Poland/Commonwealth gets huge bonuses to cavalry combat strength and cost. Hordes are hordes.
By the second half of the game period, assuming you are playing as a major power and fighting the likes of France or a properly-fed Austria, you will want reinforcement stacks following your combat stacks for major battles. A reinforcement stack is simply a pure-infantry stack that is sent in to reinforce your combat stacks and provide fresh full-strength regiments.
If your manpower pool is not very deep, and you're fighting equal powers, by the second half of the game infantry regiments should be drawn from mercenaries to reduce stress on your manpower pool.
http://www.eu4wiki.com/Army#Composition
As has already been posted, in most circumstances the ideal combat stack is:
(1) Two to six cavalry units, not exceeding your cavalry support limit;
(2) Enough infantry to fill your combat width;
(3) A full combat width of artillery; and
(4) Reserve infantry up to the supply limit to fill out casualties.
The double cost of cavalry makes cavalry-heavy armies inefficient in most circumstances. Cavalry is usually superior to infantry when the new cavalry units show up due to increasing military tech level, but it will then become outclassed by newer infantry units. If you have the income to support lots of cavalry, then the calculus naturally changes.
Artillery should never see combat casualties and massively boosts your combat and siege effectiveness. The limit for artillery is not manpower but income, and it's all too easy to go bankrupt trying to support a huge artillery train in the early game. Your combat width depends on terrain, so as has been said above, it's perfectly possible to economize on artillery. I usually try for full combat width because I cannot always guarantee an engagement in low-width defensive terrain and prefer to not lose engagements due to insufficient artillery support.
The exception to the cavalry rule is hordes and some Eastern-tech countries like Poland. Poland/Commonwealth gets huge bonuses to cavalry combat strength and cost. Hordes are hordes.
By the second half of the game period, assuming you are playing as a major power and fighting the likes of France or a properly-fed Austria, you will want reinforcement stacks following your combat stacks for major battles. A reinforcement stack is simply a pure-infantry stack that is sent in to reinforce your combat stacks and provide fresh full-strength regiments.
If your manpower pool is not very deep, and you're fighting equal powers, by the second half of the game infantry regiments should be drawn from mercenaries to reduce stress on your manpower pool.
