For hundreds of miles, there was only a thin layer of grass, suitable for grazing horses and herding sheep. Farther out, there was only a vast desert.
Therefore, the Zerg Race to the west and north were more concentrated, but their control over the territory and the scale of their Swarms were both weaker than those on the southeast side.
Thus, the Northwest became the best direction for the Capital City's defenders to stage a breakout.
But this was a breakout and migration involving hundreds of thousands, even millions, of people. Even with sufficient vehicles and fuel, it would take at least a full day for everyone to escape and evacuate completely.
And with the close connection between the Zerg Race Mother Empresses, they would surely learn of the situation the moment the main breakout assault began and rush to provide support.
