Building an effective army in EU5 is one of the most important skills you’ll learn. A well-composed army can defeat a larger, poorly-composed one. A poorly-composed army will get destroyed even against weaker opponents. Here’s what you need to know about army composition as a beginner.

The Basics of EU5 Combat

EU5’s combat system is similar to EU4’s in its fundamentals — armies fight in phases, unit types have strengths and weaknesses, and terrain matters. But there are important differences.

[VERIFY: The exact combat mechanics in EU5 — how combat width works, how unit types interact, and whether the combat system has been significantly reworked from EU4. I believe EU5 keeps the core EU4 combat model but may have adjusted unit stats and interactions.]

The key unit types:

• Infantry — the backbone of your army. Cheap, reliable, and effective in most situations.
• Cavalry — more expensive but more powerful. Best used on the flanks.
• Artillery — expensive but devastating. Best used in the back row, where it can deal damage without taking much.

The Standard Army Template

For most of the game, a good army composition looks like this:

Early game (before artillery is practical):

• 4 infantry per 1 cavalry
• Example: 8 infantry + 2 cavalry = 10 regiments

Mid game (once artillery is available):

• 4 infantry per 1 cavalry, plus artillery
• Example: 12 infantry + 3 cavalry + 5 artillery = 20 regiments

Late game (full armies):

• 4 infantry per 1 cavalry, with artillery filling the back row
• Example: 20 infantry + 5 cavalry + 10 artillery = 35 regiments

The exact numbers depend on your combat width, which increases as you tech up. The key principle: infantry fills the front line, cavalry flanks, artillery sits in the back.

Why This Composition Works

• Infantry absorbs damage and holds the line. They’re the most cost-effective unit for the front row.
• Cavalry deals high damage on the flanks, where they can outmaneuver enemy infantry. But they’re expensive, so you don’t want too many.
• Artillery deals massive damage from the back row without taking much damage themselves. They’re the key to winning late-game battles.

Managing Your Army

1. Don’t split your forces. A single large army is more effective than two smaller ones. Keep your main army together unless you have a specific reason to split.

2. Watch your maintenance. At peace, lower your army maintenance to save money. Raise it to full before declaring war.

3. Reinforce after battles. After a big battle, your regiments will be depleted. Let them reinforce before the next fight.

4. Use terrain to your advantage. Defending in mountains or across rivers gives you a massive bonus. Let the enemy attack you in bad terrain.

Common Beginner Mistakes

• Too much cavalry. Cavalry is expensive, and too much of it wastes money. Stick to the 4:1 ratio.
• Not enough artillery. In the late game, artillery is what wins battles. Don’t skimp on it.
• Splitting your army. A divided army is a defeated army. Keep your forces together.
• Forgetting maintenance. Fighting at low maintenance is like fighting with one hand tied behind your back.

The Bottom Line

Army composition in EU5 is about balance. Infantry holds the line, cavalry flanks, and artillery wins the battle from the back. Stick to the 4:1:2 ratio (infantry:cavalry:artillery) as a baseline, adjust based on your situation, and you’ll be well-prepared for most fights.

The key is to build armies that are cost-effective, not just powerful. A balanced army that you can afford to maintain is better than an expensive army that bankrupts you.