The museum is considered the second largest museum in Warsaw, as it houses the largest collection of military equipment in Poland and documents the military aspects of its history. There is also a wing of the museum building dedicated to the Polish National Museum, which contains non-military Polish antiquities. The museum displays the total worth of a thousand years of Polish military history - from the 10th century to World War II. It opened in 1920, and was expanded in 1993 with the Katyn Museum and the Museum of Polish Military Technology.