Captain is a militairy rank. A banner or a garrison is usually led by a captain. Generally the head of a non-military group (i.e. a gang of bandits) can be called captain as well. Captain is also the title usually given to the leader of the city guard.
A centurion is a non-commissioned officer (or NCO) similar to a Sergeant.
Commander is a generic term for an officer commanding any armed forces unit. In witcher universe that include generals, head of divisions, brigades, regiments, battalions, companies, free companies or smaller military units, special forces as well as commanders of guerilla or militia troops.
Field Hetman of the CrownEdit
Field Marshal is the title of a supreme commander in the Nilfgaardian military.
Jarl of SkelligeEdit
The Jarl of Skellige (Polish: jarl Wysp Skellige) is a title referring to the main commander of the Skellige military forces leading the kingdom's powerful fleet and other branches, thus making them the most faithful aide to the king or queen. Commander differs from regular clan chieftains, with single "jarl" or "earl", by small crown from what appears to be gold and silver.
The lieutenant is usually the Captain's deputy.
The lieutenant colonel is the colonel's second in command.
Major General Edit
Soldier is one who fights as part of an organized land-based armed force. A soldier can be an enlisted person, an officer, or a non-commissioned officer. The Soldier is also nomenclature for lowest rank possible in army.