The most notable member of the Treuchtlingen line was Geoffrey Henry, who reigned 1600 – 1632. In 1614 he converted to Roman Catholicism. After the outbreak of the Thirty Years' War (1618–1648), he abandoned his diplomatic career and entered the army, serving as a lieutenant-colonel at Battle of White Mountain in 1620. After being promoted to a colonel and serving with the Spanish forces in Italy and the Grey Leagues, he was sent to suppress a rebellion in Upper Austria in 1626. He later served with Tilly against Denmark and Brunswick, but his attempts to obtain the Principality of Wolfenbüttel failed. In 1628 he was awarded the title of Imperial Count alongside his distant cousin Philip of the Pappenheim-Alesheim line. In 1631 he took part in the notorious Sack of Magdeburg. He died at the Battle of Lützen in 1632.