Spoils of War is a minigame inside War Machines. You can participate as many times as you want. While the first daily participation is free - additional playthroughs on the same day cost a small fee of Diamonds each time.

The game mode consists of a series of 30 zones the player must complete one at a time. In each zone, you will be offered four cards face down - three containing rewards and one including a bomb. If you select a card with a reward (such as Diamonds, Coins, Ammo etc.) attached will add to your accumulated prizes. While choosing a bomb card will cause you to lose the challenge.

Intro Window to Spoils of War

The Zones

There are 3 different zone types in Spoils of War:

Normal:
Normal zones are the bulk of your encounters in the Spoils of War. They contain four cards, three of which are rewards and one a bomb.
Normal Zone

Safe Zone:
This zone will grant better rewards than normal zones. Safe Zones also do not contain bomb cards, meaning they are impossible to lose. Safe zones are encountered every five levels (5, 10, 15, 20, 25)
Safe Zone

Resupply Zone:
This zone will give the best kinds of rewards (even better than Safe Zone rewards) and doesn't contain bomb cards. There is only one Resupply Zones at the very end, zone 30
Resupply Zone

It should also be noted that the first zone (round 1) is also a safe zone and it's impossible to pick the bomb card there.

What happens you select a bomb card.

If you select a bomb card, a popup with a skull and an explosion pops up.
Bomb Card

In this screen, there will be the following buttons:
Give Up
You will lose the challenge, forfeit all your rewards and get sent back to the garage.

Continue
You will pay the continuing fee (which increases with each loss) and can continue from the same zone they lost. The bomb card, however, is removed from the card pool, meaning you will have a guarantee to progress to the next round.
Continue Screen

Collecting earned rewards

You can collect their prizes during the run before losing and conclude the Spoils of War session. This can be done by tapping on the "Exit" button in the bottom right corner of the screen.

Another way to collect their prizes is if you complete all 30 levels of the challenge. After completing the last zone, a "congratulations" popup with appeal and a "Collect Rewards" button.
Congratulations

Once you have decided to collect your rewards during the run or at the end, you will be brought to a unique screen. This screen will take you through each type of reward (and quantity) you have received from that run.