 Complete the following phrase:  The 7th-century Frankish Chronicle of Fredegar wrote that the Avars employed the Slavs, or Wends, as Befulci, showing that the Slavs formed special military units in the Avar Khaganate. According to the same chronicle, the Wends rose up in rebellion against their Avar masters and elected a Frankish merchant, Samo, their king in the fortieth year of Clothars reign, that is in 623 or 624. Modern historians agree that the Avars defeat during the siege of Constantinople in 626 enabled Samo to consolidate his rule. He routed the invading army of Dagobert I, King of the Franks, in the 