The enemy plans were definitely related to attacking the bunkers at the same time and overwhelm them with numbers. A lot of the people coming here were powerhouses above level 30, so their plan was obvious.
By disrupting their timing, the Alterrans could have better chances of dealing with the enemy group by group, making it a bit more manageable.
That said, the chaos alone would signal the others to come, so they'd probably arrive, and what they needed to do was to take down as many as they could before more reinforcements arrived.
Guarding the area around the bunkers with Althea were Lady Gaia, a few teams of guards, and several trusted mercenary teams. There couldn't be too many people because the area was only so big. Too many and they could hit each other instead.
Anyway, there was only one entrance to the bunkers, and that was the only thing they had to stop the enemies from approaching.
