Answer:
Aphorism
Explanation:
Anagram is a word, phrase, or name formed by rearranging the letters of another. I don't think this is it because they is no words that were rearranged.
Aphorism is a pithy observation that contains a general truth. This could be true!
Analogy is a comparison between two things. This is not it because there are not two things being compared.
Allusion is an expression designed to call something to mind without mentioning it explicitly; an indirect or passing reference. This is not it because this sentence is explicit meaning it is very straight foward.
Out of all four of those... I would go with Aphorism.
Since the flames of the gas chambers and the flames of the battle extinguished his true belief in god, he is saying that he will never forget. He will never forget the pain and suffering and his lost loved ones and all the pain he survived through.
