The population of this region has been an organic part of the Georgian state and of (Orthodox) Christian faith since ancient times. In an earlier epoch the territory of Saingilo—at that time part of the Caucasian Albanian state—lay in the northeastern part of the province of Hereti, which was settled by related tribes and communities of Georgians, known as the Heri, linked by close social-economic and cultural-historical relations that led eventually to ethnic merger. There are data that support the assertion that in the fourth to fifth centuries Hereti was already a political component of Georgia; this is corroborated by surviving Georgian cultural monuments dating to the sixth to eighth centuries. In the eleventh century Hereti was part of the saeristavo (feudal Georgian duchy) of Mach'i. At that time, Hereti became part of the principality of Kakheti (K'axeti). Kakheti and the neighboring principality of Kartli were long the principal cultural centers of feudal Georgia. After the displacement, during the early medieval period, of the central government from southern Georgia (Meskheti, Tao-K'larjeti) to eastern Georgia, these principalities came to play an especially significant role. In the fifteenth century the term "Hereti" gradually disappeared from the political nomenclature and was replaced by the word "Kakheti," which referred to Kakheti proper plus Hereti.
In the Middle Ages seven Georgian schools were in operation in Saingilo (the students were taught theology, philosophy, orthography, church history, and the history of Georgia and Albania). These schools played an essential cultural and educational role and assisted in establishing cultural relations among the peoples of the Caucasus. Literary materials were prepared in the schools for diffusion in the northern Caucasus. In the thirteenth to fourteenth centuries the use of the Georgian alphabet and Georgian Christian literature spread from Saingilo to the neighboring province of Daghestan, and churches were founded there, remnants of which can be seen today. (It should be recalled that for a long time, beginning in the fifth century, a significant part of Daghestan was within the sphere of Georgian political influence.)
In the late feudal period, in keeping with political changes in Kakheti, the region of Eliseni came into being, corresponding to the territory of present-day Saingilo. It was here, on Georgian lands annexed by the Persians at the beginning of the seventh century, that Shah Abbas created the sultanate of Elisu. During the late feudal period, the military and political interests of the powerful Near-Eastern states came into conflict in the Caucasus. The political struggle between Persia and the Ottoman Empire for dominance in Caucasia had a significant impact on the fate of the Georgian people. It had particularly adverse consequences for cultural and political relations among the peoples of the region and led to hostility between the Georgians and the peoples of the northern Caucasus. The Persians contributed to political and, in particular, ethnic and confessional changes in the area. On the periphery of Georgia, feudal lords in the Daghestanian mountains, aided by support from Persia and Turkey, conducted an armed struggle against the agricultural settlements of Kakheti. The border regions of Kakheti were settled by Tsakhurs and Avars—Daghestanian tribes referred to as "Leks" by the Georgians. The struggle for the territory of Saingilo ended in the eighteenth century with its seizure by northern Caucasian mountaineers, who established there Avarian (in the Ch'ar-Belakan District) and Tsakhurian "free communes." As a result of raids conducted by bands of Avar and Tsakhur warriors in Saingilo, the Ingilos became serfs of the Daghestanian rulers, who forced them to make pay tribute. Some Daghestanian families hired themselves out as temporary workers on Ingilo farms. In this way, gradually, by peaceful or hostile means, these tribes settled in Saingilo and colonized it. Already after the foundation of the sultanate of Elisu the conquerors had, by a concerted effort, undertaken the Islamicization of the region.
In 1803 Saingilo (that is, the sultanates of Ch'ar-Belakani and Elisu) were incorporated into the Russian Empire. As a result, the Ch'ar-Belakan District (okrug) was established in 1830, and subsequently (in 1840), the Belakan District, administratively a part of Georgia. In 1842 this district once again became a separate region (oblast), and in 1844 the Ch'ar-Belakan Military Region was founded, which included the former sultanate of Elisu (the present-day Kakheti and Tsakhur regions). In 1860 the Zakatal Region was established on this territory, forming a part of the Tbilisi Province (Tiflisskaia Guberniia), which existed until 1917. In 1920 an agreement was signed by the Russian Federated Socialist Republic and democratic Georgia, according to which Soviet Russia recognized the following territorial units as pertaining to Georgia: Tbilisi and Kutaisi provinces; the Batumi, Zakatal, and Sukhumi regions; and other territories, including a significant part of the Black Sea coastal region. Consequently, after the declaration of independence of the Georgian democracy, the Zakatal Region (Saingilo) was returned to Georgia. This turnaround in the tragic history of the Ingilos was only temporary: subsequent to the occupation and annexation of democratic Georgia by the Red Army, the ancient Georgian province of Saingilo was artificially annexed to the Azerbaijan SSR, despite the fact that the Ingilos bear no particular cultural similarity to the Azerbaijanis, a Muslim Turkic people differing from the indigenous Caucasian groups in many cultural characteristics. The joining of Saingilo to the Azerbaijan SSR was part of Stalin's nationality policy, which had the purpose of strengthening the imperial structure of the USSR. After the annexation of Saingilo the Azerbaijani element in Saingilo grew considerably. A part of the Ingilo population still retains the (Orthodox) Christian faith, but another, larger segment adheres to the Sunni sect of Islam. The Christian Ingilos dwell in Kakh District ( raion ), and the Muslims in Zakatal, Belakan, and part of the Kakh districts.
The population of Saingilo consists primarily of Ingilo Georgians, Avars and Tsakhurs, immigrants from Daghestan (Lezgins), and Azerbaijanis. There are also some Russians and others. Knowledge of the Azerbaijani language has increased among the Ingilos, but within the domestic circle they retain the Georgian language; this is especially true of Ingilo women. In recent times some Muslim Ingilos have shown a renewed interest in their ethnic origins, including a preference for Georgian rather than Muslim names.