A New Birth of Freedom: The Visitor

In the far distant future, an alien invasion has devastated earth. In the wake of the destruction, Edwin Blair finds himself drafted to travel back through time and convince Abraham Lincoln and Ulysses S. Grant to lend him their armies. Because the surviving members of the human race have discovered that the aliens are headed to the past as well, and must be stopped at all costs. Even if that means changing the future that Blair knows, and loves.

The problem is, Edwin Blair is not a warrior. He isn't a military genius or soldier. He's a historian specializing in the 1800's. However, history, as he's about to find out, is much different when you're living in it instead of just reading about it.

Now, if he can just convince the historical figures he's come all this way to see that he's not a crackpot.