Tap Rank button on the bottom of officer stats interface to upgrade officer rank.

Upgrade Rank Cost

Cost Merit Medal, the same officer or the fragments of the same officer to gain Merit and then upgrade officer rank.

The amount of Merits varies with the Merit Medal and officer which will be cost.

After the officer is cost in upgrading the rank, it will disappear.

Effect of officer's skills is improved with the upgrading of officer's rank.

Officer's skills are the major source of officer's Power.

Therefore, upgrading officer's rank is the best way to increase officer's Power.