Complex sentence: Višeslav or Vojislav, was the first Serbian ruler known by name, who ruled as the Prince of the Serbs in 780, ruling what is known in historiography as the Serbian Principality.
Split into simpler sentences: Višeslav or Vojislav (Војислав) was the first Serbian ruler known by name, who ruled as the Prince of the Serbs in 780. The polity is known in historiography as the Serbian Principality.