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At the time when Charles the Fat became the sole ruler of East Francia in 881, the sons of Wilhelm and Engelschalk, the one-time commanders of the Bavarian forces occupying Moravia in 870–871, began to conspire with various Bavarian magnates in order to eject Arbo, the margrave Louis the German had appointed to command a key part of East Francia's frontier on the Danube. Arbo, however, appealed for and received help from both Charles the Fat and Svatopluk, and even handed his son over to the latter as a hostage.