Once you decide which land card to target during a battle, you can click the "Add Troops" button to add troops to that land card. Your goal is to add enough troops to overtake the defender’s troops. If you place more troops than the defender’s troops, you win the card!
To add a different amount of troops than the default, simply use the slider to set a new number of troops. The slider will default to 1 - 300 troops. To add more than 300 troops, you can adjust the slider in increments of 300 by clicking the red or green buttons above the slider. Once you have decided on the amount of troops to add, press the "Add Troops" button.
You will see your troops added to the card and your total available troops decremented at the top of the screen. If you added enough troops to become the leader, you will see your name as the "current leader" and your "high troops" number will be the number everyone else will need to beat.
Troops that aren’t lost will remain on the card until the end of the battle, even if someone takes the card from you. When you bring additional troops to the card they will be added to “My Troops” and that total number of troops will go up against the defender’s troops.
Put simply, if you bring fewer troops than are currently on the card, you’ll lose 40% of the troops you added. Adding more troops than are what's on the card sounds straightforward, but there are ways that defenders can mask the true number of troops so be warned!