Game concept
War
The game also links it as Wars.
From the game's encyclopedia
Armed conflict is the most straightforward way to expand your Realm. However, declaring War requires a justification for doing so, called a Casus Belli. You cannot achieve more with a War than the selected casus belli permits.
Wars are won by defeating enemy Armies in Battle and Occupying enemy Holdings. Doing so will accrue War Score, eventually forcing the enemy to accept Defeat in the Peace Offer.
Regardless of the outcome of a War, the attacker gains a Truce toward the defender for a time, but the defender is free to declare a new war immediately.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
War is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Armed conflict is the most straightforward way to expand your Realm." It covers Civil War, Dominate Title and Expand Dominance. The game also links it as Wars. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.