The Army Museum re-located from Delft to Soesterberg
(
https://www.nmm.nl/)
If you are interested in 1939-1945, the Airborne Museum in Oosterbeek, just west of Arnhem, is worth a visit. Just east of Nijmegen is Groesbeek, with another Market Garden related museum. Further south there is the Dutch War and Resistance Museum at Overloon, the location of heavy fighting in late 1944 (though the official war history devotes only the proverbial footnote to it).
If you like fortresses in Vauban style, Naarden is close to Amsterdam andl has the look and feel of an old fortified town.
Amsterdam has of course plenty of museums, and nearby Haarlem is like Amsterdam but smaller and without the million or so tourists
Wienand