Thanks for contacting the World Warfare support team.
To make sure your progress is saved in Game Center, you will need to connect your in-game account to Game Center.
Game Center is simply an app that saves your in-game progress, this allowing you to access your game data on another device.
Hint: Game Center only saves one game for every account. Attempting to save more than one game to your Game Center account will result in lost data!
How to find Game Center?
1. Navigate to Settings and scroll down to Game Center
2. Click on Apple ID
3. If you already have an account, go ahead and log in. If not, create an Apple ID
4. Open Game Center from your Home Screen
5. Find the game icon and launch the game from within Game Center
You should then be prompted with a message reading “Welcome back___” with your name filling in the blank.
We hope this information is helpful in addressing your question and hope you have a nice day!