Leauges are a placement system that reflect your skill in specific game mode on a global scale. In division 1, the ultimate division, you will find the top tank fighters in the world. Each division has a set amount of games. Based on the number of games you win or lose, after you complete the games you either are promoted a division, remain in the same division, or are relegated a division. With each division, you receive rewards with every win. As you move up in divisions, the rewards grow.
Within each division, there is a set number of wins necessary for promotion, and an additional number of wins which is slightly higher, which is the number of wins necessary to receive a medal. Once you've won enough games to be promoted to the next division, there is also the opportunity to continue playing in order to win a medal. This is only possible if within the balance of games, you can achieve enough wins to receive a medal. If you have the opportunity to win a medal, you will continue playing. If not enough games remain to allot you the opportunity to achieve enough wins for a medal, you will be automatically promoted a division.
For example, take one division with 20 games total, 13 wins required for division promotion, and an additional 5 wins required for a medal, making it 18 wins total. If you win your first 13 games, you will continue playing with the hopes of winning a medal. If you lose your first 3 games and then win 13, you will not continue to play as with your 4 game balance you can not win the 5 games necessary for a medal.