The border had been proposed by the Great Powers in the London Protocol of 1829 as the northern boundary of an autonomous Greek state under Ottoman suzerainty, but when the full independence of Greece was agreed on in the London Protocol of 1830, the borders of the new state were reduced to the Aspropotamos–Spercheios line, only to be again expanded in the London Conference of 1832, which was confirmed by the Treaty of Constantinople (1832).