Poetry has long been a medium that has communicated the concerns of the heart and mind during times of crisis, and one subject that has motivated many poets to reach for their pen is war. Many of the world's great poets have written eloquently about the violence and madness of armed conflict, among them Walt Whitman, Langston Hughes, Wilfred Owen, Sherman Pearl, and Siegfried Sassoon among many others, and in 2003, when Laura Bush invited a group of poets to visit the White House for a symposium on American verse, author Sam Hamill responded by founding an activist group called Poets Against the War, and persuaded many of the participants to contribute verse that denounced American military policy. Filmmaker Rick King has examined the link between poetry and anti-war protest in the documentary Voices in Wartime, which looks at how many writers have used their poems as a vehicle of protest, the events that promoted poets to speak out, and how the tragic consequences have inspired both experienced and novice writers alike.