Quizro uses Harry Turtledove's Guns of the South as an example of alternate history. While there is no doubt that providing the Confederacy with AK-47s has a pretty dramatic impact on the war, the fact that AK-47s aren't 19th century weapons and the fact that the introduction of the AK-47s requires the use of a time machine would seem to me to make the book more of a pseudo-historical story or possibly a science fiction story rather than an alternate history story.

Strictly speaking, an alternate history story explores the consequences which follow from one or more (typically) quite minor changes to historical events. For example, Harry Turtledove's How Few Remain novel hinges around the consequences of an event involving Confederate General Lee's Special Order 191.

Prepared by Lee in September of 1864, Special Order 191 describes Lee's plan to invade Maryland as part of an advance northwards. In real life, a copy of this order was found by the North's General McClellan which allowed him to inflict a series of key defeats on General Lee and his army.

In the book, the first four pages describe how a soldier picks up and returns an envelope which a Confederate courier has dropped. The envelope, of course, contains a copy of Special Order 191. The rest of the book is an exploration of the consequences of this relatively minor incident (i.e. something doesn't get lost).

Without giving too much of the story away, some of the consequences are:

All in all, it's an interesting story and, unlike Guns of the South, the story doesn't rely on 20th century firearms or time travel or any other external interference with history.

I'm sorry but I don't like handing out spoilers so you're going to have to read the book if you want to know what else happens (this is also not intended to be a review of the book).

How Few Remain; by Harry Turtledove; copyright © 1977 by Harry Turtledove; a Del Rey book published by The Ballantine Publishing Group; ISBN 0-345-40614-1 (paperback edition)

If you're interested in alternate history, you might also want to read the books that follow How Few Remain:

The Great War: American Front
The Great War: Walk in Hell
The Great War: Breakthrough
American Empire: Blood and Iron
American Empire: The Center Cannot Hold
P.S. I quite enjoyed Guns of the South. I just don't think that it's an example of alternate history.