In late 1225 or early 1226, shortly after the assassination of Archbishop Engelbert II of Cologne, Count Rudolph of Coevorden with an army of Drenthers invaded Groningen, taking advantage of a dispute between the burgrave Egbert and his relatives, the wealthy Gelkingen. Egbert was an ally of Bishop Otto II and the Gelkingen were involved in trade, but the "Deeds of the Bishops" does not give a reason for their conflict. Rudolph took the side of the Gelkingen and there was, according to the "Deeds", "civil war in Groningen" ("civili guerre in Groninge").