 With the establishment of a dynastic union with the Grand Duchy of Lithuania in 1386, it became customary to use two banners—Polish and Lithuanian—as equally important insignia of royal authority.In the mid-16th century, before the creation of the Polish-Lithuanian Commonwealth (real union) in 1569, a single banner for the entire entity also came into use.The Commonwealth banner was initially plain white emblazoned with the arms of the Commonwealth which combined the heraldic charges of Poland (White Eagle) and Lithuania (Pursuer).