East Frisia
Rudolf Christian of Ostfriesland, Count of East Frisia, was count of East Frisia, (Hage, 2 June 1602 – Hage, 17 April 1628) and the second son of Enno III, Count of East Frisia and Anna of Holstein-Gottorp. During his reign, foreign troops participating in the Thirty Years' War began retreating into and quartering in East Frisia. Also during his reign, fen exploitation in East Frisia begins.