The Army Museum (Muzeum Wojska w Białymstoku) covers the military history of the Podlasie region from the 18th century through the post-war period, with particularly strong sections on the two world wars and the Polish-Soviet War. Uniforms, weapons, partisan equipment, and a courtyard full of armoured vehicles and artillery pieces.
It is a serious museum rather than a glossy one — labels are mostly in Polish, with some English — but the WWII material on the Białystok district underground (one of the most active in occupied Poland) is excellent and not covered elsewhere. Closed Mondays.