With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: Deeply depressed when Moira broke off their engagement because of her new job, Xavier began traveling around the world as an adventurer after leaving the army In Cairo, he meets a young girl named Ororo Munroe (later known as Storm), who is a pickpocket, and the Shadow King, a powerful mutant who is posing as Egyptian crime lord Amahl Farouk. Xavier defeats the Shadow King, barely escaping with his life. This encounter leads to Xavier's decision to devote his life to protecting humanity from evil mutants and safeguarding innocent mutants from human oppression. 
text_B: What rank did Xavier hold in the armed forces?
DON'T KNOW.