What do shields do?

What is the point of the shields in your cities in Civilization II? I know that they are related to the amount of soldiers you can have, but how do I find out those numbers? They don't seem to be on the units themselves. Also, are they related to the city's defense?

Solution 1:

Blue shields in the city view correspond to the production value of the city, they don't have anything to do with soldiers. This corresponds to how quickly the city can produce units and buildings.

Soldiers have separate shields that show their allegiance (by colour) and their health (by amount filled).