Demand Troops
2.0 Update:
For the 2.0 update, the demand troops research was removed from the tech tree. In all worlds with 2.0 or higher implemented, the demand troops option for farming is available automatically after you upgrade the village to level 3. See New Farming System for more information.
Demand Troops
Demanding troops is the same as demanding resources but you get troops instead of resources. You may also get units unavailable to your current barracks.
To send off a troop demand run you must do exactly what you do when sending off a normal attack. Click on the village you would like to demand troops from on the map, and then go to the attack tab at the top. Next select the troops you want to send to the chosen village and then instead of selecting the "resource looting" option or any of the other options, make sure you select the option that states "request troops". From there just select the attack button and before you know it, troops should be rolling in.