Task: Question Answering
Input (English): Passage: The mid-19th-century patriarch of the Hungarian-Jewish Sonnenschein family is a tavern owner who makes his own popular distilled herb-based tonic in Austria-Hungary. The tonic, called Taste of Sunshine, is later commercially made by his son, Emmanuel, bringing the family great wealth and prestige. He builds a large estate where his oldest son, Ignatz, falls in love with his first cousin, Valerie, despite the disapproval of Emmanuel and Rose. Ignatz, while studying in law school, begins an affair with Valerie. Ignatz graduates and later earns a place as a respected district judge, when he is asked by the chief judge to change his Jewish surname in order to be promoted to the central court. The entire generation – Ignatz, his physician brother Gustave and photographer cousin Valerie – change their last name to Sors ("fate"), a more Hungarian-sounding name. Ignatz then gets promoted when he tells the Minister of Justice a way to delay the prosecution of corrupt politicians.
In the spring of 1899, when Valerie becomes pregnant, she and Ignatz happily marry before the birth of their son, Istvan. Their second son, Adam, is born in 1902. Ignatz continues to support the Habsburg monarchy, while Gustave pushes for a communist revolution. Both brothers enlist in the Austro-Hungarian Army as officers during World War I. In the days after the war, Valerie briefly leaves him for another man, the old monarchy collapses, and Ignatz loses his judicial position under a series of short-lived socialist and communist regimes in which Gustave is involved. When a new monarchy emerges and asks Ignatz to oversee trials of retribution against the communists, he declines and is forced to retire. His health deteriorates rapidly and he dies, leaving Valerie as head of the family. 
Question: What are the names of the brothers who enlist in the Austro-Hungarian Army as officers during World War I?
Output (English): Istvan.