Growing prestige as a painter brought changes in his life and work. Though he continued his earlier themes, Bellows also began to receive portrait commissions, as well as social invitations, from New York's wealthy elite. Additionally, he followed Henri's lead and began to summer in Maine, painting seascapes on Monhegan and Matinicus islands.
At the same time, the always socially conscious Bellows also associated with a group of radical artists and activists called "the Lyrical Left", who tended towards anarchism in their extreme advocacy of individual rights. He taught at the first Modern School in New York City (as did his mentor, Henri), and served on the editorial board of the socialist journal, The Masses, to which he contributed many drawings and prints beginning in 1911. However, he was often at odds with the other contributors because of his belief that artistic freedom should trump any ideological editorial policy. Bellows also notably dissented from this circle in his very public support of U.S. intervention in World War I. In 1918, he created a series of lithographs and paintings that graphically depicted the atrocities committed by Germany during its invasion of Belgium. Notable among these was The Germans Arrive, which was based on an actual account and gruesomely illustrated a German soldier restraining a Belgian teen whose hands had just been severed. However, his work was also highly critical of the domestic censorship and persecution of anti-war dissenters conducted by the U.S. government under the Espionage Act.