The Ivanhoe Gambit

Sometimes Sergeant Major Lucas Priest wondered why he had enlisted in the U.S. Army Temporal Corps. Fighting in the Time Wars wasn't the easiest way to make a living. Sailing with Lord Nelson, battling Custer at Little Big Horn, and a year of pillaging with Attila and his Huns had left him ready for a vacation.
But a demented scheme to impersonate the King of England was threatening to change the course of history. Two army teams had already failed to intercept the madman. So Lucas and his men must clock back to the twentieth century to try and prevent an irreversible split in time.
But when Lucas discovers whom they were to impersonate, he almost wishes that Hannibal had killed him back in Carthage. How were Ivanhoe, Robin Hood, and a band of merry outlaws supposed to protect the future of the world?