A Junior General couldn't be looked down upon. In fact, beside being a potential Heir, it was the highest ranking a youth of the Viola Bloodline could have.
When a world reached a certain level, especially for the Viola family's that had reached the pinnacle of its potential, the only way to grow and expand was by conquering the lands of other worlds. Of course, the best way to do this wasn't by fighting it out with worlds at your level. Rather, the best way was by targeting worlds beneath you.
Lower level worlds had certain protections. That came either from tacit agreements, protection by higher level worlds, and/or natural barriers.