The Adventures of Conrad Stargard: 5-volume Set (The Cross-time Engineer, The High-Tech Knight, The Radiant Warrior, The Flying Warlord, Lord Conrad's Lady)

Conrad Schwartz was a faithful Roman Catholic and a stalwart "socialist" of the Peoples' Republic of Poland, 20th century. Hiking in the mountains, a trifle hung over, he found himself running for his life from a Teutonic knight! It wasn't the DT's. He really was back in the 13th century, and since he did not know how he got there, he had no hope of returning. So he made the best of it, through six delightful volumes. He slowly, slowly civilizes his country hundreds of years early, and even establishes an Explorer Corps to check out the rest of the world, with an emphasis on raw materials. But try as he might, he just cannot convert these old-timers to the version of communism that he thinks of as "socialism!"