Invasion! was a series created by Pat Mills and mostly written by Gerry Finley-Day that appeared in the first 51 editions of the weekly comic 2000 AD. The series introduced the character of Bill Savage, a classic anti-authoritarian character of the type which Mills is best known for.
Serbia in the Middle Ages refers to the medieval period in the history of Serbia. The period begins in the 6th century with the Slavic migrations to Southeastern Europe ,  and lasts until the Ottoman conquest of Serbian lands in the second half of the 15th century.