Two synods, in 255 and 256, held under Cyprian, pronounced against the validity of heretical baptism, thus taking direct issue with Stephen I, bishop of Rome, who promptly repudiated them. A third synod in September 256, possibly following the repudiation, unanimously reaffirmed the position of the other two. Stephen's claims to authority as bishop of bishops were sharply resented, and for some time the relations of the Roman and African sees were severely strained.