428th Assault (Clan Steel Viper)
|428th Assault Cluster|
|Unit Profile (as of 3074)|
|Nickname||The Striking Serpents|
|Parent Formation||Gamma Galaxy|
The Steel Vipers won the right to re-take Twycross during the Fifth Wave of Operation Revival. The attack was undertaken by the 423rd Assault, 428th Assault and Ninety-Fourth Battle Clusters. Landing under the cover of the Diabolis sandstorms, the 423rd and 428th defeated the Tenth Lyran Guards RCT by using the Viper's Maw tactic, while the Ninety-fourth engaged the Ninth Federated Commonwealth RCT and forced them back to the spaceport. The battle was over in a matter of hours.
The cluster took heavy losses on Tukayyid, firstly against the Sixth Division at Devil's Bath; needing to be rescued by Zeta Galaxy. Subsequently it moved against the fresh 321st and 401st Divisions. This time it was shattered holding the ComGuards at bay. The 428th was almost wiped out on Tukayyid.
War of Reaving
On Londerholm in 3072 the 428th Assault Cluster along with Gamma Galaxy ran up against forces of Clan Coyote and the Society. During the prolonged battle Gamma made a devastating flank charge, but the 428th took heavy casualties in the victory.
In September 3074 a large Viper force of four Galaxies arrived at Tokasha. Finding Clan Blood Spirit forces in a position to take the entire planet the Vipers called their own Trial of Possession for it. The Blood Spirits had three Galaxies on planet and the Vipers landed all four of their to oppose them. The assault by Gamma Galaxy overran the defensive line of the Spirits' Omega Galaxy allowing Alpha Galaxy to push on to the Blood Spirits headquarters killing their Khan.  After the battle Gamma was disbanded and the 428th Assault Cluster was transferred to Delta Galaxy.
The Vipers launched a massive assault on against Clan Coyote on Tamaron in December 3074 with six Galaxies and a large naval force. The Viper warships opened up holes in the Coyote SDS allowing the DropShips a path through. Alpha Galaxy led the way but it wasn't long until all six Galaxies had made planetfall despite the fierce aerospace attacks. A swift assault by Delta Galaxy helped to secure the landing zone. The ground forces made for their objectives, several major factory complexes in the Apache Mountains, then it attack turned toward the planetary capital of San Mateo By 16 December the city was surrounded. Four Coyote Galaxies had been destroyed, but at the cost of three of the Viper's own including Delta and the 428th Assault Cluster.
428th Assault Cluster 
- Cluster Command Star (1 OmniMech Star)
- Trinary Alpha (3 OmniMech Stars)
- Trinary Bravo (3 OmniMech Stars)
- Trinary Charlie (1 OmniMech/Elemental Nova, 2 Elemental Stars)
- Trinary Delta (3 OmniMech Stars)
- Trinary Echo (3 OmniFighter Stars)
428th Assault Cluster - Veteran/Reliable 
- 5 Trinaries
428th Assault Cluster - Elite/Reliable 
- 90% full strength and fully equipped with OmnMechs
- Invading Clans, p. 88, "Fifth Wave" - Twycross
- Field Manual: Warden Clans, p. 145, "428th Assault Cluster"
- Invading Clans, p. 86-87
- Objective Raids, p. 30
- Field Manual: Warden Clans, p. 165
- Field Manual: Update, p. 80
- The Wars of Reaving, p. 106-107
- The Wars of Reaving, p.138-139
- The Wars of Reaving, p.143
- Wars of Reaving, p. 142-143
- Invading Clans, p. 95