What is the most likely reason why an author would include a sidebar in his or her report? To expand upon ideas presented in the main text. To take up space when the author is out of ideas to write. To present new information that is unrelated to the main text. To give the reader the author's opinion of a topic.

the answer is: the start of world war i, and russia’s hopes of benefiting from it

during world war i russian joined due to in their current crisis they were being supported by france and the war was already declared to them by germany, they needed to maintain their political goal and leadership role in the balkans, and is the same feeling that this excerpt evoke the eager of maintain the land value.