Skirmishes on the frontier between Hungary and the Holy Roman Empire first occurred in 1050. Emperor Henry invaded Hungary in August 1051, but Andrew and Béla successfully applied scorched earth tactics against the imperial troops and forced them to withdraw. Legend says that the Vértes Hills near Székesfehérvár were named after the armours—vért in Hungarian—which were discarded by the retreating German soldiers.

Andrew initiated new peace negotiations with the emperor and promised to pay an annual tribute, but his offers were refused. Next summer, the emperor returned to Hungary and laid siege to Pressburg (Bratislava, Slovakia). Zotmund, "a most skilful swimmer" scuttled the emperor's ships. After Pope Leo IX mediated a peace treaty, the emperor lifted the siege and withdrew from Hungary. Andrew soon refused to fulfill his promises made under duress, and even allied with Conrad I, Duke of Bavaria, a prominent opponent of Emperor Henry III.