The Russian Empire in 1914 was a vast, backward absolute monarchy that extended right across present-day Ukraine, Belarus and Poland. Most people lived mediaeval lives, as subsistence farmers, in small villages or in poorly-developed towns. It seemed to the Germans a region ripe for improvement. The trouble was, "improvement" would mean replacing the Russians and Poles who lived there with Germans.
The imminent collapse of Russia eventually alarmed the United States into joining Britain and France in deploying troops. German divisions which had been fighting against Russia could now be entrained to fight in the West. It was believed that American soldiers would be required to shore up the Western Front against the expected German offensive.