The objective here is to kill an enemy foreman. After about 20 minutes or so of playing any map, the AI will start sending foremen into your estates to try and capture your properties.
You can tell when this is happening due to a flashing icon appearing in the bottom left corner of the screen that looks as though it has hazard tape on it.
Your best bet it to click the icon to take you to the scene of the crime. It will take a bit of micro management, but you will need to locate your nearest work crew and move them into the garden. Select individual builders with
and target the enemy foreman. The icon changes to four flashing arrows. Press
to get your selected builder to attack the foreman.
It's important to note a couple of things. Firstly, DO NOT try and use your own formant to attack. He won't, but selecting him and trying to get him to attack will stop any builder currently fighting with the foreman to stop what he's doing.
Secondly, the enemy foreman will try to escape as soon as your builders start attacking, so try and stack them up on him quickly. It may take a couple of attempts before the foreman is killed.