Bob Dylan’s song ‘John Brown’ is an anti-war lyric. It tells the story of an American mother who sends her son John Brown to war on some foreign land. The song follows the young soldier and his mother’s lives. The singer shows us the true fate of the American soldiers who are stationed in foreign countries for war. 
 
The poem has vividly depicted the contrast between the romantic ideals of war and its reality. We see that the mother is very proud of her son as he is going to fight for his country. There is a sense of heroism and patriotism. That is why she wants to show everybody in her area that her son is a hero. 
 
But the contrast starts rolling out when in the fifth stanza, the poet says “Then the letters ceased to come”. And the gap between reality and romanticism comes clear in the sixth stanza of the poem when she at last sees her son and “she could hardly believe her eyes”. Then the poet gives us an image of the soldier’s pain and horrific experience in the war by describing his face as “blown-off” and a metal brace around his waist.
 
So, by this song, Bob Dylan clearly builds a bridge between fancy and reality, as suggested in the question. He also questions the very nature of war and shows us that there is no nobility in warfare, thereby strengthening the idea of pacifism.