You could earn Medals of Valour inside the Tactical Chests: you will unlock permanent upgrades with these event chests which will help not only in your events but in all your prisons. The chest will always provide a fair amount of card fragments. The Medal of Valour could appear in any of these chests as an extra card.
Those medals are cumulative and will provide 100 extra recruits to your counter automatically. You can accumulate as many medals as you wish, but they must be spent during the ongoing event, or they will be lost.
You can find your medal counter by tapping on the red event widget. There you will be able to use your medals (tapping on USE button) and open new tactical chests (tapping on OBTAIN button).