History of Gdynia
After the 1919 Treaty of Versailles, the town was renamed Gdynia and, with other parts of the then-German Empire, were ceded to Poland and became known as "Polish Corridor". At Versailles, also, the Danzig city and surrounding area were declared Free State Danzig (of which Gdynia was not a part) under the League of Nations and under Poland's control.
Poland subsequently built a huge military and commercial harbour at Gdynia. By 1934, the Gdynia harbour had overtaken the former largest Prussian harbour at Danzig in terms of size. Poland also built up its military presence significantly in the area.