The Battle of the Anvil is a large battle that takes place between the Polity and the Union at the Anvil in 2072. The battle would result in an unexpected victory for the Polity, thanks to the late Rufus Weller.
The battle begins when a Behemoth and Nemesis appears, seemingly out of nowhere. Nemesis contacts Weller and demands that Julian Chase's consciousness be destroyed and to be returned to his organic body, but he is interrupted by an attack from Chase operating his Holon. During this exchange, Raquel Marin asks Able about the status of the Hammer System. Able informs her a test fire could be performed in 10 minutes. The rest of the Union force appears shortly afterward, and the Anvil then deploys its forces, including the Holons of gen:LOCK squad. Kazu Iida is nearly captured in his Holon, but he manages to break free with his close combat skills augmented by gen:LOCK phase two with Valentina Romanyszyn.
As the battle rages outside, specialized Union craft breaches the Anvil's walls, deploying troops and Union Drones into its interior. The Polity replies with security forces. Weller informs gen:LOCK squad of the danger and orders them to return to their transports and download to protect their bodies. Chase focuses on his duel with Nemesis, stating his body could not physically run. Weller provides Kazu and Valentina with weapons and instructs Caliban to protect them, but he remains in the lab, apparently to delete the information stored on gen:LOCK.
After Union forces enter the lab, Weller detonates an explosive device, killing himself and all Union forces present in the lab. The gen:LOCK squad take a lift to the barracks, but just after they get off, they notice a large number of Union troops approaching their position. Cameron MacCloud uses Mixed Reality to briefly hide the team from them. Caliban and the gen:LOCK squad then ambush and incapacitate the Union soldiers before continuing their escape. As Miguel Garza helps drive them to their transport, Nemesis notices Chase's tank in the back of a truck and breaks away from Chase. He charges at the truck, but three Striders stop him, and Chase attacks him again. The Behemoth nearly reaches The Anvil's main structure and fires a salvo of missiles. Most are destroyed by point defense, but one gets much closer to the command center until Chase redirects it at the last second. Able informs Colonel Marin that the Hammer System is ready, and she orders for it to fire in on the Behemoth. This destroys it, but the triumph proved short-lived, however, as it releases Nanotech that floods over the defenders and through the breaches in the Anvil. Yasamin Madrani pilots the transport away from the battle, escorted by Chase.
Despite the losses on both sides of the conflict, the battle unexpectedly ends up in favor of the Polity. Weeks prior to the battle, Weller discovered that the reason the Nanotech do not harm any Union forces and sympathizers is due to a chip emitting a signal that exempts them from being attacked by it.
After the discovery, Weller informed Colonel Marin his discovery about said signal alongside his idea about how to mimic it. When the Nanotech enters the base, the Vanguard decided to utilize his idea for the first time. The signal worked, and the Vanguard are able to wipe out the remaining Union forces in the area.