Military units

Throughout The Witcher series, many different military units exist, sometimes changing names depending on the country.

Banner
A banner is a cavalry unit of 200 mounted men, led by a captain.

In the real world a banner was usually associated with a unit between 200-400 troops; it is possible that infantry banners exist and possibly fall on the upper end of the scale due to the comparative inexpensiveness of foot soldiers.
 * Dun Banner

Brigade

 * 2nd Vicovaro Brigade
 * 7th Daerlan Brigade
 * Impera Brigade
 * Nauzicaa
 * Vrihedd

Division
A division is a formation within an organized army or large military unit.
 * Alba Division
 * Ard Feainn Division
 * Deithwen Division
 * Frundsberg Division
 * Magne Division
 * Venendal Division

Free Company
A Free Company refers to an army of mercenaries (or condottieri) officially acting independently of any government, for whoever will pay, thus the word "free" in their name meaning free of any particular allegiance. This type of mercenary group is most popular in Redania.

In The Tower of the Swallow, king Esterad Thyssen of Kovir and Poviss released some political prisoners formerly known as the "Sly cats" on the condition that they support the efforts to push back the Nilfgaardian invasion at the battles of Mayena and Brenna.
 * Lyrian Free Company
 * Adieu's Free Company
 * Angren Free Company
 * Shevlov's Free Company
 * Redanian Free Company

Regiment

 * Morteisen Battle Group
 * Sievers Battle Group
 * Vreemde Battle Group