For months Alliance forces had been luring the Swarm towards Caldera at great loss of life. A vast expanse of land had been effectively depopulated, resources had begun to run low, and the Swarm seemed as strong as ever. Caldera was humanities last chance to survive.
Dunehill and the First Aristoc Grand Army, along with the majority of the Peacekeeper powered armour units, took the centre of the defences within the crater. Their flanks were held by FTU and Matriarchy forces, dug in to the town of Caldera itself, long since evacuated and repurposed into a fortress. Much of the remaining strength of the Alliance was some distance away, ready to move in and seal the trap. The exceptions to this were the last of the bait units, the hardiest and experienced troops, luring the vast Swarm force in. Pre-battle estimates were that the bait teams had successfully lured over 90% of the Swarm to Caldera .
The first elements of the Swarm entered the valley at approximately 9:15am. By this point only 12% of the bait teams were still alive. The valley was a little under a mile and a half long, 5% made it to the defences in Caldera.
9:42am - The defences engage the Swarm.
10:10am - Primary minefield is depleted. Swarm still entering the valley.
11:15am - First circle of defences are abandoned.
11:27am - Scouting units report last Swarm have entered the valley. Reinforcements move to seal valley.
11:50am – First line of defences overrun. Estimate 20% casualties within crater.
1:24pm – Reinforcements in position. Engage Swarm in the rear.
1:55pm – Second defence line overrun.
3:35pm – Defences around the town of Caldera fail. House to house fighting erupts. Peacekeeper 2nd Armoured Division moves to reinforce.
4:17pm - Tactical Fusion Weapon detonated in Caldera settlement.
4:18pm – Defenders fall back to last defence line. Casualties of defenders estimated at 76%, casualties of reinforcements at 24%.
4:39pm – Visual contact made between reinforcements and initial defenders.
4:53pm – Final defence line overrun. Hand to hand combat is observed in Dunehill’s Forward Command post.
5:01pm – Tactical Fusion Weapon detonated at Forward Command Post.
6:18pm – Last Swarm Eliminated. Reinforcement Casualties at 49%, defence casualties at 97%.