The Fresco of Guidoriccio da Fogliano

Detail from Simone Martini's fresco of Guidoriccio da Fogliano at the Siege of Monte Massi in 1328 at Scala/Palazzo Pubblico, Sienna. (I don't know exactly when the picture was painted, but Martini's dates are 1284-1344, so it must have been pretty soon after the 1328 siege.)

Thanks to Bob Charrette, who first found this picture for me.
Thanks also to Emil Kren and Daniel Marx of the Web Gallery of Art, whose clearer and more complete scan (above) I copied from their Web page on Simone Martini.