When the Big Two completed their centuries-long preparation and openly invaded the Red Ocean with great momentum, the human warfleets largely encountered little resistance at first.
Part of that had to do with the starting point of their invasion. The Mech Trade Association and the Common Fleet Alliance hadn't built the crucial gateway between the galaxies in the middle of the dwarf galaxy, but instead opted to place it in the periphery.
The concentration of resources was much lower here, which meant that the major alien races of the Red Ocean did not have a high presence in this neighborhood. The warships they utilized in the surrounding regions were second-line assets at best and were far from matching the highest standards of their respective civilizations.
