The Polish Army Museum in Warsaw preserves a large number of exhibits devoted to the history of Polish military. The main exhibition is divided into different rooms, each devoted to an epoch in Polish military history, starting from the Middle Ages, through the Renaissance and early modern era, to the Napoleonic wars and the Polish uprisings in the 20th century. The story is continued with uniforms and weaponry of the Polish campaign of 1939 and the struggles of various Polish military formations, which ultimately led to the liberation of the occupied countries in Europe. One room is especially devoted to the Second World War. In this section the visitor may get acquainted with uniforms, hand weapons, smaller equipment and numerous other items belonging to Polish soldiers who took part in the liberation of Western Europe, Italy and Poland. Apart from the indoor exhibition, there is a collection in the open air of military vehicles, artillery pieces, combat aircraft and helicopters, which at various stages were used by Polish military formations. The museum has two other facilities in Warsaw, one of which is devoted to a moving exhibition about the Katyn Massacre in April and May 1940, when the Soviet secret service NKVD murdered over 20.000 Polish intellectuals and military officers. Plans for a new museum building are made. The museum will be turned into a modern multimedia institution, with larger exhibition space and modern facilities. The current building will then be taken over by the National Museum in Warsaw.