Special Designation Unit

A Special Designation Unit is a unit in the Terran Army with a particular status. These units are the most elite units within the army and their recruitment and training methods are often unique. SDUs are most often divisions. 
The first SDU is generally considered to be the the Custodian's Sword which existed during the Custodian's reign from 2055 to 2125. It served during the Unification Wars. During this period it became the most effective military unit in the world, having the best equipment and training possible for the period. At the time the division did not officially have a Special Designation as the concept did not exist yet. The unit was disbanded following the Custodian's death according to his wishes. However several governments in the second half of the 2100s wished to revive the concept of super-elite units. In 2176 Special Designation Units were officially established. 
There are currently 30 SDUs in the federal army. Out of these, 16 are divisions, 1 is a corps and 13 are brigades. The divisions are all inspired by historical units of distinction and bear a nickname. For example, the third SDU established in 2196 is the 82nd Airborne "All-American" division. Six of the divisions are officially "Legions" and independent from any army corps. The 13 brigades are all HERAKLES brigades and are considered the most elite units in the galaxy. The Special Designation Units are:
*Corps:
**1st army corps "Excelsior" of the 1st Terran Army, 2176
*Divisions:
**1st Infantry division "The Custodian's Sword", 2176 (part of 1st army corps "Excelsior") 
**442nd Infantry division "Nisei", 2176
**369th Infantry division "Hellfighters", 2176
**First Legion "Hispana IX", 2178
**Second Legion "Victrix VI", 2178
**Third Legion "Gemina VII", 2178
**Fourth Legion "Fulminata XII", 2183
**Fifth Legion "Gallica III", 2184
**Sixth Legion "Augusta II", 2184
**82nd Airborne division "All-American", 2196
**101st Airborne division "Screaming Eagles", 2196
**1st Armoured division "The Companions", 2199
**7th Armoured division "Ghost Division", 2202
**77th Infantry division "Lost Battalion", 2218
**1815th Infantry division "Gurkhas", 2225
**1568th Infantry division "Caroleans", 2286
*HERAKLES units (brigades):
**HERAKLES I, 2336
**HERAKLES II, 2356
**HERAKLES III, 2356
**HERAKLES IV, 2406
**HERAKLES V, 2406
**HERAKLES VI, 2406
**HERAKLES VII, 2406
**HERAKLES VIII, 2599
**HERAKLES IX, 2599
**HERAKLES X, 2635
**HERAKLES XI, 2635
**HERAKLES XII, 2635
**HERAKLES XIII, 2635