Game concept
Military Budget
The game also links it as Military.
From the game's encyclopedia
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.
Military Budget is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Treasury sent to military Province Vassals from the central government, for the purposes of funding additional military activities." It is part of Budget Category. The game also links it as Military. Patch 1.20.1.2, from game/common/game_concepts/tgp_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/tgp_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.