WARNING this review does contain spoilers about the series.
The Lost Regiment is a story about a Union Civil War regiment that gets pulled into some sort of inter dimensional portal or a wormhole. They are sucked across time and space and deposited in a strange world name Valennia that is filled with humans from all over the globe and from every period of history.
But humans are not the only inhabitant of this strange new world that the 35th Maine
The first people the regiment encounters on this new world are the Rus, a people descendent from Russians from the middle ages. They live in a rigid caste system of peasants, boyors(lords) and the church in a very similar fashion to what their ancestors did. This system is what has kept the Rus people “alive” under the rule of the Boyors and there Tugar overlords. With the introduction of the “Yankees” as they become known to the Rus people everything changes especially for one peasant named Kalenka. He sees the potential that the Yankees bring to his world the potential for change and the potential to fight back against the boyors and the Tugars that keep them in power.
The events that follow in the first book and the books after all spring from a simple desire for freedom that the Rus people have and that the Yankees are capable of making it a reality. You follow along as the old order is overthrown and the Yankees begin the arduous task of bringing up the Rus to a level of Civil War technology that gives them an edge against the highly trained and massive Tugar army.
The characters are memorable as well the with the story being told from multiple view points as different important event take place across the landscape. My favorites are Colonel Andrew Keene, Vincent Hawthorne, and the leaders of the various Hordes they fight. Much of the human side of the story is told from the view of Colonel Keene. You read how he struggles with the decision he made both during the Civil War on Earth and this new war he is drawn into on Valennia
Another human character that I enjoyed following was a private called Vincent Hawthorne. He is a pacifist Quaker boy from Pennsylvania but he believed in freedom so much that he joined the Union army to fight for it. He undergoes the most radical change of anyone in the story from a timid Quaker boy to the cold-blooded killer and talented general he becomes later.
Finally you watch the leaders of the hordes as they struggles with the new reality of cattle that fight back, with cattle that kill their men, with cattle that destroy a people and traditions that go back centuries just so they can have their freedom. They have never encounter cattle such as the men of the 35th and the 44th and as such they cannot comprehend why they do not simply submit. The opposing beliefs and desires of these two people clash head to head as the titanic struggle between them unfolds. The Hordes facing an enemy that must win or perish.
I have only found this series online though it may be available at your library if it has a well stocked science fiction section or access to a network of book collections.