What theme or message is bradberry conveying a sound of thunder

blank verse is often confused with free verse. free verse avoids traditional poetic forms such as rhyme schemes and conventional metres and can follow any pattern the poet wishes which means that the verses and lines can differ in length as the poet chooses. however blank verse like free verse is also unrhymed but each line in blank verse has roughly the same number of stresses and syllables, usually following the iambic pentameter

the speech this question is referring to is president kennedy's special message to the congress on urgent national needs, may 25, 1961

kennedy responds in a very direct and concrete way to those thinking that communism is a positive system:

"yet their aggression is more often concealed than open. they have fired no missiles; and their troops are seldom seen. they send arms, agitators, aid, technicians and propaganda to every troubled area. but where fighting is required, it is usually done by others--by guerrillas striking at night, by assassins striking alone--assassins who have taken the lives of four thousand civil officers in the last twelve months in vietnam alone--by subversives and saboteurs and insurrectionists, who in some cases control whole areas inside of independent nations." (kennedy)

president kennedy presents communism as cowardly, as a hidden and treacherous weapon that strikes from the shadows like thieves, he represents the system as not even being capable of showing and open and overt attack or confrontation. to finish up the response, he expresses that the system attacks even a country's idependence and freedom.