To the ramparts -- the assault's about to come.

The National Gallery launches its thunderous Cezanne show on Sunday, then the Hirshhorn Museum follows up with a huge salvo of works by Japanese photographer Hiroshi Sugimoto, to which the National Gallery adds a barrage of art by Marcel Duchamp and his friends in the dada movement, all accompanied by artistic volleys from the Phillips Collection, the Textile Museum and the smaller Smithsonian battalions.