And generated primarily via combat.
4UC is formulated in such a way that it adds 1 UU and 1 not-UU
- A UU is defined as anything capable in participating directly in combat by either doing damage directly or augmenting your army via auras etc.
- The other slot is defined by being literally anything else. A UB, a UNW and a UI obviously are incapable of participating in combat (with the possible exception of UIs via AOE damage, but they are still not selectable). A civilian unit like a worker, settler, diplomat, or great person that is incapable of participating in combat would also occupy one of these not-UU slots.