Criminal activities offer a way to earn enough money to build up an army.
In order to start initiate criminal activities, you will need to gather criminal units.
Those gathered criminal units are non-military and can only be used in the underground.
To make money with those units, you will have to order them to commit crimes in the underground screen of a town. There are several branches of crime, each one having different characteristics and levels. A higher level always comes with a larger income.
The duration of a criminal activity always remains the same, no matter how many groups of criminals are active. Once the duration passes, you will receive the exploited money and the activity starts again.
If you assign more units to a branch of crime than the maximum allows, you won't receive a larger income. Those additional units only count as further protection against competitors.

In order to commit high-level crimes, you have to gain criminal fame by gathering units, but for the most part by successfully completing your acts of crime.
With your fame increasing, you will begin gathering more and stronger units. The strength of a unit however will not have an influence on the money that is gained.
The criminal fame spreads from within a city and extends to the country border. The major part of the fame is put together from the town in which your crimes take place, but also from its home country.
The higher the level of your criminals action is and the more money you earn from it, the faster your fame will rise.
Once you have reached the fame level 3, you can organize gangs in the underground in exchange for money if you have the need. With every further fame level you can choose stronger units.

Criminal activities will also affect the political fame of presidents and mayors, but in a negative way.
In order to defend themselves against it, a president can initiate several ordinances.
Keeping an ordinance active costs money, initiating an ordinance will cause additional costs.
Every branch of crime can be fought with one of four different ordinances.
Once active, an ordinance will have the following effects on all towns within the country, as long as there is no disorder:
In the underground of a town there can be several crime lords active at the same time.
Players, who are criminally active in a town, will be listed among the "Criminal Bigwigs" within the underground screen of the town as soon as their criminal fame reaches level 3.
Whenever there is a branch of crime with two active players having assigned more criminals than the maximum, it will result in an underground conflict within that branch.
If you want to expel another player from business in the underground altogether, you can issue a streetfight using the underground screen. In a streetfight all active criminal units will take part, regardless of the activity they are assigned to.
After a conflict is over, all of the criminal activities, that do not have the required minimum of units assigned to, will be aborted.

In every town you can become the godfather once you have reached the criminal fame of level 5.
If you should try to become godfather when there already is another one present, he will have to be challenged in a streetfight and has to be defeated.
Having a godfather in a town will have the following pros and cons:
Every player has the choice to deny this tax on the underground screen.
You can do this for the whole country, in a single town or towards the player who is currently godfather.
If the godfather tax is denied, all of the effects of having a godfather will be void.