Helena, the most economic prosperous city in Montana. It's home to the gold stockpile and the gold mines that they owned. The Brotherhood was keen on securing the city's economic power in order to benefit future trade outside of the state. The Brotherhood troops came quickly and surrounded the down. The militia numbered less than 300 so it was easy to quickly overwhelm them with firepower and numbers. Fighting was brief before the militia commander surrendered to the Legate. The Legate walked through the state capital and saw the large shops and markets but also the restored memorials and the city hall where the city council had been awaiting for their invaders.
The leadership had heard what happened to Billings and said that they wanted to negotiate tribute. The Legate gave them a chance to negotiate, but only one. The deal for the tribute was more in the way to favor the city but they knew that they can leverage gold as something that the Brotherhood wanted. It was, but they also wanted more practical tribute, which they will also provide.
With two cities pacified, the final one stood at the sight of the Brotherhood's victory. Once the cities fell, the techno-Legion would be able to swarm across the eastern half of Montana, knowing that no small community would dare to fight back against power-armored troopers who could level entire settlements with just a mere order.
The soldiers prepare to march on the last city, and then the whole state in the name of Mars and Brotherhood.