Alzeco 1 was dux of the Bulgars ("Vulgarum dux, Alzeco nomine"); during the reign of king Grimoald 3 (662/671) he left the rest of his people and led his army into Italy peacefully, asking Grimoald 3 for permission to settle and enter his service ("incertum quam ob causam, a sua gente digressus, Italiam pacifice introiens, cum omni sui ducatus exercitu ad regem Grimuald venit, ei se serviturum atque in eius patria habitaturum promittens"); Grimoald 3 directed Alzeco 1 to Beneventum, where the king's son Romoald 1 gave Alzeco 1 abandoned territories at Saepinum, Bovianum, Isernia and other cities to settle in and also gave him the (Lombard) title of gastald instead of that of dux ("ipsumque Alzeconem, mutato dignitatis nomine, de duce gastaldium vocitari praecepit"); according to Paul the Deacon, the descendants of these Bulgars still lived in those areas in his own day (late eighth century), speaking Latin but also retaining the use of their own tongue: Paul. Diac., Hist. Lang. V 29.

Alzeco 1 is probably identical with Alciocus, a Bulgar leader who escaped a massacre in Bavaria with some seven hundred men and their families and fled to live many years among the Wends; previously he had fled with other Bulgars from the Avars in Pannonia to Gaul and sought refuge with Dagobert (Dagibert 1), who settled them in Bavaria but then organised the massacre: Fredegarius, IV 72 and see PLRE III, p. 40 (Alciocus).

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