To command troops in the field, in Victoria 3, it takes Generals. You are the overseer of all the operations, but the tactics are their field of expertise, and choosing them wisely may win you the war.
Generals are characters who command Servicemen and Officers into battle on Fronts. Every country will start the game with one or a few Generals - many of them straight out of the history books - and can recruit more as needed.
Generals are recruited from Strategic Regions, and gain command of as many locally available troops in that region that their Command Limit allows. Command Limit is determined by their Rank, which ranges from 1-star to 5-star. If several Generals are headquartered in the same Strategic Region, the troops are split up between them proportional to their Command Limit as well.
Military operations can be complex to manage and to model this every General costs a certain amount of Bureaucracy to maintain. You can promote Generals freely, but while higher-ranking Generals can effectively command more troops they also cost more Bureaucracy.
Like other characters, such as Heads of States and Interest Group Leaders, Generals have a set of Traits that determine their abilities and weaknesses. Admirals, their naval counterparts, work the same way. All characters have a Personality Trait, with different effects depending on what role they fill. For example, a Cruel General might cause more deaths among enemy casualties, leaving fewer enemy Pops to recover through battlefield medicine or return home as Dependents, while a Charismatic General might keep their troops’ Morale high even when supplies run short.
Characters may also gain Conditions due to events or simply the passage of time, as can be seen in the above image. These often affect the character’s health, but might also influence their popularity or ability to carry out their basic duties. Shellshocked is a classic example of a Condition your General might gain.