Antoninus Pius recognizes the king of the Quadi, who becomes an ally of Rome, in 140.
The Quadi and Marcomanni, perhaps originating north of the River Main had migrated into what is now Moravia, western Slovakia and Lower Austria where they had displaced Celtic cultures and were first noticed by Romans in 8–6 BCE, briefly documented by Tacitus.
In his Germania, Tacitus only mentions the Quadi in the same breath as the Marcomanni, alike in warlike spirit, alike governed by "kings" of their own noble stock, "descended from the noble line of Maroboduus and Tudrus," the "Tudric" line apparently kings among the Quadi.
The royal powers of both tribes are also alike, according to Tacitus, in being supported by Roman silver.
Their neighbors are the Marcomanni to the west, proto-Slavic tribes to the north, Sarmatian Iazgyians and Asding Vandals arriving to the east somewhat later, and the Roman Empire to the south.