Helmguard was a loyal subject of the Empire. They were concerned at an uprising in a neighbouring state (who's name is now forgotten) caused by an hitherto undetected Anathema. The Anathema was supported by an enormous number of Beastmen from the beyond the threshold.
Unable to face the threat alone, Helmguard requested assistance from the Empress. A cohort of the Vermillion Legion were dispatched with orders to assist the Wyld hunt in their duties.
The Wyld Hunt is a specific faction who hunt down and kill reborn Anathema. Usually (under the guidance of the Empress) they hit their targets before they become a threat. In this case half a dozen Dragon-Blooded were dispatched.
The Cohorts instructions were to destroy the Anathema's forces whilst the Wyld hunt targetted the Anathema himself.
Upon reaching the capital, the Cohort were initially confused when asked by the locals when the rest would be arriving. However, on seeing the quality of the local intellegence reports they sent their own request for assistance from the empire.
The leader of the Wyld hunt was not interested in waiting for reinforcements. He order the Cohort to attack the anathemas forces. Unhappy but unwilling to disapear a direct order the leader of the Vermillion company ordered his men to move out - and were astonished when they received assistance from the locals. Their initial attacks proved very successful, but disaster struck when the leader of the Wyld Hunt sent orders insisting they slowly retreat to the capital.
The commander of the Helmguard forces saw that this was folly and would not be responsible for leading the enemy to his cities gates. As such he agreed to attack the enemy to buy the Cohort time to make it back to the City. At dawn he marched to glory - they were never seen again. The Cohort returned to the city and began fortifications.
Half the Wyld hunt returned (with something head shaped in the bag) and after reprovisioning left orders for the Cohort to hold and destroy the remaining enemy forces.
For three months they held the city, surviving wave after wave of Beastmen attack. Stockpiles running low, the people were starting to lose hope. On the hundreth day of the seige, they woke in the morning to see that the Beastmen had vanished.
Trackers showed indications that the host had returned to the North. No one knew why.
The Cohort had been reduced to a mere 100 men. They owed the local people a debt, and, in theory at least, had not yet completed their last order. So the decision was made that they would stay and help rebuild Helmguard. The local’s were more than happy to see them stay.
100 years have passed but the beastman hordes still periodically come charging down from the "Cursed Land" to the North where the Anathema's forces were based. They seem to have no real interest in holding land merely pillaging and killing.
To the West there are the remainder of a couple of City-States that were devastated by the Anathema's forces. They hold Helmguard responsible for the attack and therefore aren't particularly friendly.
To the East the City-states have gradually been assimilated in a fairly large state known as Tyranus. At the moment Helmguard is considered to big a bite for them, but they have been worrying the borders for the last 50 years or so.