March of Pannonia

The Bavarian prefects had to face the rising threat by the Moravian ruler Mojmir I, who pursued separatist policies in the Eastern March.

This march, already called marcha orientalis, corresponded at its core to a frontier along the Danube, from the Traungau and the former Slavic principality of Carantania to Szombathely and the Rába River including the Vienna basin.

Two years later, King Louis ceded the march directly to his son Carloman of Bavaria, who had the fortifications of Herzogenburg and Wilhelmsburg erected along the Traisen River by the Wilhelminer margraves William and Engelschalk I.

When his father Louis died in 876, Carloman succeeded him as East Frankish king and gave Lower Pannonia to his son Arnulf of Carinthia.

From 882, the rule was enfeebled by the Wilhelminer War of Margrave Engelschalk II against the Aribonids, whereafter Prince Svatopluk I of Moravia took the occasion to invade the Pannonian lands.