Your combat division is based on your activity points — measured against all other active players.

You earn activity points automatically for almost everything you do in the game. Every Wednesday at 12:00 all active players are ranked by their activity points for that week: the higher you place, the more combat division points you're awarded — the most active players get the most, scaling down from there. After that, the weekly activity points reset to zero.

Unlike activity points, combat division points accumulate over the weeks. Each division requires a certain amount of them — once your total crosses the next threshold, you move up. At the same time, a portion of your combat division points decays each week, so you can also drop back down if you're less active for a while.

That's why a single strong week or a high activity figure doesn't automatically promote you: what matters is staying near the top over time, so that your weekly gains outpace the decay. Reaching the very top takes consistently being among the most active players. Diamonds don't buy a promotion.