Tap Upgrade button on the bottom of officer's attribute interface to upgrade an officer.

Cost Training Dummies or other officers to gain EXP and then upgrade the officer.

After upgrading, the cost Training Dummies and other officers would disappear.

After the top level is reached, the extra EXP wouldn't be kept.

After the officer is upgraded, the Leadership and Special Operation Squad stats of the officer would be improved.

The sum of marching officers' Leadership and the number of marching troops in Parade Ground determine the number of all the troops in marching queue.

The stats of Special Operation Squad has a direct influence on DPS and HP of officers in Special Operation.