 Henry lead his first military campaign as sovereign in 1040 into Bohemia, where Bretislav I posed a threat, who intended to establish a separate archbishopric.After having attended the reform sessions of a number of monasteries, Henry summoned his army at Stablo, In July he joined with contingents at Goslar and deployed his entire army at Regensburg.He set out on 13 August and was soon ambushed in the passes of the Bohemian Forest and forced to retreat with heavy losses at the Battle at Brůdek.