Iranian Azerbaijanis
According to Russian scholar Rostislav Rybakov, Iranian Azerbaijan was almost fully Turkicized by 14th and 15th centuries, though the local population left its mark in the Azerbaijani culture and language and the ethnic border between the Turkish people and Azerbaijanis was established in the 16th century. In 1900, Joseph Deniker, wrote that Azerbaijanis of Caucasus and Iran, who spoke a Turkic language, of the same physical type as Persians, who spoke an Iranian language.