Frederick of Isenberg

[2] Before the split between Arnold of Altena-Isenberg the eldest and his brother Friedrich Altena-Mark the younger son of Everhard von Berg-Altena.

According to recent research, Frederick of Isenberg was a leading figure in the opposition of Westphalian nobles to the aggressive power politics of the Archbishop of Cologne,[3] Engelbert of Berg.

During their return together from Soest to Cologne, Count Frederick arranged to ambush his cousin, in a defile at the foot of the Gevelsberg between Hagen and Schwelm in the late afternoon of 7 November 1225, in the course of which the Archbishop was killed.

Current research assumes the latter, and that it was intended to take him into "knightly detention" so that the political demands of the opposing nobility could be pushed through.

Frederick travelled with his brothers Dietrich and Engelbert, bishops of Münster and Osnabrück (both also implicated in the death of the Archbishop), and the notary of Isenberg with the necessary documents to the Curia in Rome, in order to have the excommunication lifted.