The Battle of Coenenberg was fought during the Germanian invasion of Eylstadt as part of the World War. The Germanian 169th Infantry Division's invasion of the town was ultimately repelled, mostly due to Izetta's entry into the battle.
To the surprise of the Eylstadians, the Germanians attacked Eylstadt from the west, previously feigning another attack. As the Germanian threat became more dangerous, barrage balloons were placed around Landsbruck, Eylstadt's capital. General Schneider informs Rudolf of the fall of Fort Schwiezen, and the fate of its garrison, as well as his plans to repel the Germanians at Coenenberg, but Sieg doubts the possibility of a victory.
A sergeant in Jonas' platoon notes that the nearby castle contains a large amount of equipment dating back to the Middle Ages, including spears, lances, and swords. These would soon be used by Izetta to fight off the Germanian army.
See: Episode 3
Near the outskirts of Coenenberg, a small force of Eylstadian FT-17 tanks fought against Germanian Panzers in a one-sided battle. The FT-17s were obsolete and hopeless in the face of superior Germanian technology and numbers, and were quickly wiped out.
A wave of Germanian He-111 bombers was deployed to strike the Eylstadtian defensive positions. The Germanians expected this airstrike to wipe out the enemy force. Despite suffering severely from the bombardment, the Eylstadtians withstood the bombing. This prompted the Germanians to deploy ground troops supported by a Panzer tank company to clear the area.
The Eylstadtian defenders were unable to hold the line for long and were forced to fall back. The Eylstadtian artillery, which remained unscathed during the initial bombing, and proceeded to bombard the Germanian forces, delaying their advance.
Izetta requested to be allowed to enter the battle, but her offer to fight was initially turned down by Fine, who did not want to risk her in battle. A number of Eylstadtian troops from Fort Schwiezen also requested to be allowed to join the fight, but Fine refused, knowing that the soldiers already engaged were dying just to buy time for nearby civilians to evacuate.
The Germanians dispatched a squadron of Stukas to destroy the enemy artillery. However, the Stuka squadron is attacked by Izetta, who uses lances as guided missiles to shoot down the Stukas. After using up all her lances, Izetta then proceeds to take a large number of swords from the nearby castle, before returning down to engage the enemy. The Germanians suffer devastating losses at the hands of Izetta, losing an entire company of tanks.
Fine and the troops with her notice the turn of the tide in the battle. Fine uses this and rallies the Coenenberg troops via morse code, leading the troops to victory over the Germanian army.
The battle was a major victory for the Eylstadtians, greatly raising the Eylstadtian army's morale. The bedridden Rudolf is informed about Finé's safety and Izetta's deeds just before he passes away. Izetta would be known as a savior by the Eylstadtian people, and her power was advertised to the world, in an indirect maneuver to deter the Germanian invasion. However, Berkman notes that Izetta, while powerful, wasn't invincible, and his intelligence task force continued to work to exploit her weakness, which was narrowly covered up in Veile Pass.