This is Kurt von Hammerstein-Equord‘s special classification scheme for his men:
I divide my officers into four groups. There are clever, diligent, stupid, and lazy officers. Usually two characteristics are combined. Some are clever and diligent — their place is the General Staff. The next lot are stupid and lazy — they make up 90 percent of every army and are suited to routine duties. Anyone who is both clever and lazy is qualified for the highest leadership duties, because he possesses the intellectual clarity and the composure necessary for difficult decisions. One must beware of anyone who is stupid and diligent — he must not be entrusted with any responsibility because he will always cause only mischief.
Interacting with large groups of people daily enables me to see not only the importance of good, i.e., intelligent, leadership, but also the danger of stupidity.
Beware of those who are stupid, ambitious, and seeking positions of power.