You can access Military Drill and manage your time through the Camp Board. At Military Drill, you will be taken to Imperium Factory to save 8 people there and guide them into the truck.
You have to look for fuel to drive a truck. If you manage to save everyone, you will get a reward of 4,000 New Dollars, 16,500 Combat Mastery Points and 400 Camp Contribution.
There is a lot of military supply in the Empire Factory that you can get including Land Mine and Molotov. There will be a red area in the Factory marked, you must save the person in the red area first before being bombarded.
Beware because every hostage you have to save is guarded by the Imperial Soldier who can kill you in an instant! There are many types of Imperial Soldiers including Flamethrower, Bazooka and Sniper.
You can kill Imperial Soldier by planting a Land Mine in the place you have determined and then fishing them to where the Land Mine is planted. Or, you can throw Molotov at them.
If there are lots of Snipers, you need a place to take refuge. Don't overlook the Sniper because they are too difficult to kill and you will throw lots of bullets.
When you successfully release the hostages, take the hostages towards the truck and don't forget to refuel as needed. After everything is ready, you can leave the area by driving the truck.
Hostages who have been rescued will stay in your Camp and they will raise Prosperity from Camp.