This sprawling museum located in a former 19th-century military school 1km north of Taksim has a huge collection of militaria dating from the 13th century to recent times. Objects include everything from Ottoman armour to Atatürk's underwear. Sadly, many exhibits (most notably the WWI rooms) lack English labelling. Try to visit in the afternoon so that you can enjoy a concert by the Mehter military band, which plays most days between 3pm and 4pm.
The large museum is spread over two floors. On the ground floor are displays of weapons and Turkish military uniforms through the ages and old-fashioned dioramas of major battles, including one of the Conquest.
The upper floor has a hall devoted to Atatürk, who was a famous Ottoman general before he became founder and commander-in-chief of the republican army and first president of the Turkish Republic. Also here are two small rooms on the Dardenelles War (aka Gallipoli campaign) and a room with displays about the so-called 'Armenian Issue' that some visitors may find offensive.
Perhaps the best reason to visit this museum is to view the short concert by the Mehter. Turkish historians argue that the Mehter was the world's first true military band. Its purpose was not to make pretty music for dancing, but to precede the conquering Ottoman ±è²¹ÅŸ²¹²õ (governors or generals) into vanquished towns, impressing upon the defeated populace their new, subordinate status. Children in particular will love watching the band members march with their steady, measured pace, turning in unison to face first the left side of the line of march, then the right.
The easiest way to get to the museum is to walk up Cumhuriyet Caddesi from Taksim Meydanı. This will take around 20 minutes. Alternatively, take any bus heading up Cumhuriyet Caddesi from Taksim.