This is a website with articles about the Assyrian (Syriac) history and identity.
Syriac is a collective names of several Syriac speaking churches. It is a linguistic term, and not an ethnicity. According to the Great historian and Patriarch of the Syriac Orthodox Church, Mor Mikhael Rabo: the Syriac Church in the Middle East is made of two groups Assyrians and Arameans. Assyrians live in Upper Mesopotamia (Beth Nahrain) East of the Euphrates River, while Arameans live in the Levant West of the Euphrates River. The Euphrates River establishes the border line between land of Ashur and land of Aram.
Syriac Orthodox Patriarch Mor Mikhael Rabo (Michael the Great) (1166-1199 A.D.):
"So, one can see that Syria was to the west of the Euphrates, and that the name "Syrians" is applied by way of metaphor to those who speak our language, the Arameans, of which the Syrians are only one part; the others all live east of the Euphrates, that is from the banks of the Euphrates all the way to Persia. And from the banks of the Euphrate towards the East, there have been numerous kings. In Assyria: Bel and Ninus and their many successors; in Babylon: Nebuchadnezzar, who maintained in the Aramaic language with the magicians who had been summoned for the explanation of the dream; in Edessa: family of king Abgar [...]... It was shown instead that the Chaldean and Assyrian kings who were called Syrians belonged to this people"
East of Euphrates the Assyrian heartland in Upper Mesopotamia (Beth Nahrain) (northern Iraq, northeastern Syria and southeastern Turkey)
West of Euphrates the Aramean heartland in the Levant (western, southern and central Syria)