WoWS is having a special promotion where you can redeem codes for special missions to earn signal flags and cammos. Here are the list of codes for the NA server (redeem in the premium shop):
Yamato: 210815SUCHABIGSHIP
Battle of tsushima: 150715NOTHSFSHIP
Hornet: 020316SUCHABUZZSHIP
Aurora: 301116REVOLUSHIP
Midway1: 040117BETWEENSHIP
Midway2: 050117BETWEENERSHIP
Arctic Convoy1: 160217GOTOUSSRSHIP
Arctic Convoy 2: 230217VERYCOLDSHIP
Bofors: 230817GUNSFORANYSHIP
Maille-breze: 120218OUESTLESHIP
They should be active until early March!