The Vassal Swarm Meta Explained

One of the most powerful strategies in EU5 is the "vassal swarm"—creating multiple small custom vassals instead of directly conquering territory. Here's why it dominates the meta and how to use it.

What is the Vassal Swarm Strategy?

The vassal swarm involves creating 3-5 small custom vassals (2-4 provinces each) from conquered territory instead of integrating that land directly into your nation. Each vassal operates semi-independently, handling their own province development while remaining loyal subjects.

Think of it as outsourcing the tedious work of province integration, religious conversion, and cultural assimilation to AI vassals who handle it automatically—while you focus on expansion and optimization.

Why is This Strategy So Powerful?

1. Automatic Integration & Conversion

Vassals automatically integrate and convert their provinces over time. You don't need to assign cabinet members to slowly integrate conquered territories—the vassal's AI does it for you.

When you eventually annex the vassal (after 10+ years), you receive already-integrated or already-cored land without spending any of your own integration time. This dramatically accelerates your expansion speed.

2. Levy Recruitment from Unaccepted Cultures

You can only raise levies from provinces with your primary or accepted culture. But vassals can raise levies from their primary culture—even if you don't accept it.

This means a vassal with Andalusian primary culture (which Castile doesn't accept initially) can raise Andalusian levies for you, effectively giving you access to manpower you otherwise couldn't use until expensive culture acceptance or slow assimilation.

3. Cultural Opinion Trick

When you create a custom vassal with a "problem" culture as their primary (like Andalusian from Granada conquests), you can improve cultural opinion with that vassal nation.

This reduces the cultural capacity cost to accept that culture from 5.7 down to 2.8 or less. By the time you annex the vassal years later, the culture may be cheaply accepted or already converted, eliminating the discrimination penalties.

4. Faster Integration Through Size Bonuses

Smaller vassals integrate faster due to EU5's size-based integration speed bonuses. Five 3-province vassals will integrate much faster than one 15-province vassal, even though the total land is the same.

This creates a strategic incentive to create many small vassals instead of few large ones.

How to Implement the Vassal Swarm

Step 1: Conquer Territory

Win a war and occupy the provinces you want to turn into a vassal. Don't core them directly—you'll release them as a vassal instead.

Step 2: Create Custom Vassals (2-4 Provinces Each)

In the peace deal, use the "Release as Vassal" option to create a new vassal nation from the conquered provinces. Aim for 2-4 provinces per vassal—small enough for fast integration, large enough to be stable.

Example Castile vassal swarm:

• Andalusia: Created from Granada's provinces (Andalusian culture)
• Alentejo: Created from southern Portugal (Portuguese culture)
• Valencia: Created from eastern Aragon (Valencian culture)
• Barcelona: Created from northern Aragon (Catalan culture)
• Navarre: Diplomatic vassalization or conquest (Basque culture)

Step 3: Let Them Work

Once created, your vassals will automatically:

• Integrate conquered provinces to core status
• Convert provinces to your state religion
• Assimilate or promote their primary culture populations
• Raise levies for you from their culture group
• Build infrastructure (sometimes—AI varies)

You don't need to micromanage any of this. They handle it while you focus on your next conquest.

Step 4: Annex When Convenient

After 10-20 years (depending on size and integration speed modifiers), annex your vassals through the diplomatic interface. You'll receive fully integrated, already-cored provinces without spending cabinet member time or integration effort.

Which Nations Benefit Most?

The vassal swarm strategy works for any expansionist nation, but it's particularly powerful for:

• Castile: Conquering diverse Iberian cultures (Andalusian, Basque, Catalan, Portuguese)
• France: Expanding into Italy, Iberia, and Germany with multiple culture groups
• Ottomans: Managing conquered Balkan, Greek, and Middle Eastern territories
• Austria/HRE nations: Dealing with the fragmented German culture groups
• Any large empire: The more you expand into diverse cultures, the more valuable vassals become

The Trade-Off: Micromanagement

The main downside of the vassal swarm is increased diplomatic micromanagement. You'll need to manage:

• Vassal loyalty and opinion
• Integration timing (knowing when to annex)
• Diplomatic relations slots (each vassal consumes one)
• Vassal wars (they may get attacked or drag you into conflicts)

However, the efficiency gains far outweigh this micromanagement cost for most players. The vassal swarm is meta for a reason.

Master This Strategy

Understanding and implementing the vassal swarm strategy is one of the clearest markers of an intermediate-to-advanced EU5 player. It represents optimizing conquest efficiency, understanding culture and integration mechanics, and thinking several steps ahead.

Try it in your next Castile campaign. Create Andalusia, Valencia, and Navarre as vassals, and watch how much faster your empire grows compared to direct integration. You'll never go back to the old way.