You must look to Pablo Neruda and his suspiciously titled Hymn to the Glories of the People at War. Here is one brief bit (in Spanish). Here is a broader index of related poems. The visual presentation of the material is beautiful. Here is English-language background on Neruda in the war. Here is Neruda as Chilean diplomat to Spain. Here is a dual English-Spanish presentation of one part of the poem.
In my eyes, once you get past Rilke, Yeats, Eliot, and the 1920s, Paul Celan and Wallace Stevens are the only twentieth century poets who compare to Neruda.