 He used his old ideas to design the new North German war ensign with heavy involvement of the Prussian King, leading to numerous changes, like the inclusion of the Iron Cross in its original shape.The flag that was finally adopted became the war ensign of the German Empire after its founding, similar to the North German merchant ensign.The German war flag, which was slightly changed twice during the Wilhelmine Period (see gallery below), was in common use in World War I.