In the country were oil is the primary source of income, a war is about to unfold and this is all because of the ruthless prime minister. The prime minister is so strict that his underlings aren't happy with how he manages things. The rebel got piss-off and kidnap four hostages that holds a high position in the government. If these hostages are not rescued, a war will unfold and the country will be in the middle of war. That is not a great thing since the country will not benefit from a war. A country that bathes in old have its stable source of income and would not like something like that to stop their source of income.
Your mission is to protect the truck from enemies. Fire at will whenever you see enemies getting close to the truck. Each kill will earn you money and you can use it to buy some new guns, hire defenders, and upgrade the truck. Aside from the usual grenade and oil leak, which you saw on Warzone and 2, there is the spike that you can use. Also you can equip your defenders with a much powerful weapon. There is also the mounted weapon on the truck to make things easier for you.