Conrad Stargard is the protagonist and title character in a series of time travel novels written by Leo Frankowski. In them, a Polish engineer named Conrad is sent back in time to the 13th Century where he has to establish himself and cope with various crises including the eventual Mongol invasion of Eastern Europe. Leo Frankowski is a Polish-American writer of science fiction novels, and now a resident of Russia. ...

The character of Conrad has at times been described as a Mary Sue, and some aspects of the novels can be looked at as authorial wish-fulfillment. Mary Sue (or simply Sue) is a pejorative expression for a fictional character who is an idealized stand-in for the author, or for a story with such a character. ...

The series originally consisted of 4 books, with a 5th released shortly later to wrap up loose ends. They are:

• The Cross Time Engineer
• The High Tech Knight
• The Radiant Warrior
• The Flying Warlord
• Lord Conrad's Lady

all originally published by Del Rey Books, and recently being released by Baen Books. Del Rey Books is a branch of Ballantine Books, which is owned by Random House. ... Baen Books is an American publishing company established in 1983 by SF publishing industry long-timer Jim Baen. ...

A later sequel, Conrad's Quest For Rubber is set in the same world/timeline as the original series but does not feature Conrad as its protagonist.

Another book of Frankowski's, Conrad's Time Machine is set in the same universe as the original series and is only loosely related, having to do with the invention of the time machine with which Conrad ends up in the 13th century.

In late 2005, Frankowski self-published Lord Conrad's Crusade with Conrad Stargard as the protagonist. Despite being laden with typographic errors, it is true Leo Frankowski SF at it's machismo best.