While internal strife can be a constant headache, the world outside your borders is rife with opportunities and dangers. External threats in Crusader Kings III come in many forms, from ambitious neighbors and opportunistic raiders to the ever-present threat of holy wars and invasions.
Neighboring Rulers: The Most Common Foes
Your immediate neighbors are your most frequent adversaries. They will often eye your territory with covetous intent, especially if you are perceived as weak or if they have a strong claim on your lands. Diplomacy is key here. Forge alliances through marriage, use your spymaster to uncover plots, and be prepared to defend your borders. Sometimes, a preemptive war to secure your territory or seize a valuable duchy can be the best defense.
Raiders and Hostile Forces
Certain regions and cultures are prone to raiding. Norse pagans, for example, are notorious for their coastal raids, seeking plunder and disruption. These can be a nuisance, but if left unchecked, they can weaken your provinces and drain your treasury. Ensure your coastal counties have adequate defenses and consider raising your armies to meet them head-on. Larger-scale invasions, such as those from the Mongol Empire or the various Crusades and Jihads, represent existential threats that require significant military might and often broad alliances to overcome.
Holy Wars and Crusades/Jihads
Religion plays a significant role in driving conflict. When a ruler of a hostile faith declares a Holy War, they are aiming to seize territory of your faith. These wars can be devastating, as they often involve large armies and can spread rapidly across multiple duchies. Similarly, if your faith has the necessary tenets and a suitable leader, you can initiate Crusades or Jihads to conquer lands for your religion. Defending against these requires strong alliances, a well-trained army, and often a significant amount of piety and gold.
Claimants and Usurpers
External threats can also arise from individuals with claims on your titles, even if they are not your direct neighbors. A distant relative with a strong claim might gather support from fore rulers to press their case. Similarly, ambitious individuals might attempt to usurp your throne. Your spymaster is invaluable in uncovering these plots. You can counter them by improving your own legitimacy, strengthening your alliances, or by directly confronting and defeating the claimant's forces.
Managing Your Military
Regardless of the source, effectively managing your military is crucial for dealing with external threats. This involves raising levies, recruiting men-at-arms, and using powerful knights. Understanding the strengths and weaknesses of different unit types and ensuring your commanders have high martial skill can turn the tide of battle. Always keep an eye on your treasury; prolonged wars are expensive, and a bankrupt realm is an easy target.