Osip Mandelstam, Zbigniew Herbert, Anna Akhmatova, Wilfred Owen, Siegfried Sassoon, Isaac Rosenberg, Anna Swir, Mahmoud Darwish, Miguel Hernández, Federico García Lorca, Rafael Alberti, Nâzim Hikmet, Yannis Ritsos, Yehuda Amichai, Adrienne Rich, June Jordan, Muriel Rukeyser, Audre Lorde, Serhiy Zhadan, Refaat Alareer, Raúl Zurita, Yusef Komunyakaa, Ilya Kaminsky. So many others. Carolyn Forché’s anthology of the poetry of witness, Against Forgetting, is a good place to start.