In 1914 Nash began painting in oils with the encouragement of Harold Gilman, whose meticulous craftsmanship influenced his finest landscapes. Nash's most famous painting is "Over the Top" (oil on canvas, 79.4 x 107.3 cm), now hanging in the Imperial War Museum. It is an image of the counter-attack at Welsh Ridge on 30 December 1917, during which the 1st Battalion Artists' Rifles left their trenches and pushed towards Marcoing near Cambrai. Of the eighty men, sixty-eight were killed or wounded during the first few minutes. Nash was one of the twelve spared by the shell-fire, and painted this picture three months later. "The Cornfield", held by the Tate Gallery, was the first painting Nash completed that did not depict the theme of war. The picture with its ordered view of the landscape and geometric treatment of the corn stooks prefigures his brother Paul's "Equivalents for the Megaliths". Nash said that he and Paul used to paint for their own pleasure only after six o'clock, when their work as war artists was over for the day. Hence the long shadows cast by the evening sun across the middle of the painting.