Robin Burton is a young man who grow with everything anyone can hope for, immense talent for cultivation, sharp mind, a wealthy family that will stop at nothing to protect and nurture him. He had everything except the willingness to take them. "Why would I take the same route as my ancestors ? why should I become stronger? to beat this and compete with that..?! THAT IS NOT WHAT I WAS BORN FOR!!" Robin didn't want to compete with young masters, so he made an army and started invading planets.
*kachaa*
"Supreme General, I feel ashamed that you had to come to the north again. There was another severe attack wave in another area on the northern side, and I had to focus all my attention there and ignore what was happening, but this does not deny that it was negligence on my part. I bear full responsibility."
Caesar nodded and did not try to console him. The role of the defenders was to prevent the enemies from entering the formation and to confront any upcoming attack while the role of the offensive wing of the army in this case was to push the enemy army back as much as possible and make them feel threatened every time the draw close in order to reduce the pressure on the defensive wing.
Enemies getting close to this point means the attack system failed to do its job.