Bonuses for units

Hey everyone. If I want two or more "main defense" units. How do I make the new ones have a +defense in cities and defense lines. I can't find that in the bonus list. Thanks.

You can't

Ok. Thanks. Also, do you know how to set some countries to contain infantry by default and some contain milita by default?

Countries contain infantry by default if they have income of 500 or over.