1635: The Eastern Front is an alternate history novel written by Eric Flint and David Weber. The action takes place in a world where, as a result of the events that took place in the 17th century, a portal to the past was opened. The book tells about the events that take place in 1635, when a group of American technologists and military decided to support the defense of Eastern European principalities against the intervention of the Ottoman Empire. The book "1635: The Eastern Front" not only interestingly reveals the military and political aspects of that time, but also manages to combine them with incredible adventures, ideas and deep reflections on the possibilities of the development of history in alternative realities. This is a fascinating combination of historical facts and fantastical possibilities that will delight not only lovers of alternative history, but also fans of the adventure genre."