It means he wants to improve the defenses.
Something "robust" is stronger than typical items of the same type.
I have only had social contact with a couple of General Officers,but I can tell you there is no such critter as one who thinks neither his defensive or offensive capabilities can't be improved.
It's just the nature of the beast.
BTW,this does NOT mean he lacks confidence in the ability of he and his men to defend their positions. It just means that to THESE people,nothing is EVER as good as it could be. It is the nature of their occupation to think like that.