The conquest and integration of the Caucasus into the Russian Empire lasted an entire century. At the request of the Christian nations of Georgia and Armenia, leaguered hard by their Muslim neighbors to the South, the Ottoman Empire and Persia, Russia began expanding over the ridge of the Central Caucasus. In 1801 Russia incorporated the kingdom of Eastern Georgia, controlling only a single mountain route which led to her new territory. For many years the "Georgian Military Highway" remained the sole link between Russia and Georgia, constantly threatened by the elements and by mountain tribes which had not yet been subdued by Russia. The Empire continued to conquer ever more parts of the Caucasus, while, at the same time, waging wars against the Ottoman Empire and Persia. Civil engineers from Russia, among them numerous Western Europeans, fought for decades against both the nature and bandits on the highway.
Initially, Russia was not able to profit from this expansion, but nevertheless continued her push to the south. She tried to subdue the unruly mountain peoples in the west and east of the Central Caucasus by pushing military lines towards them and resettling or expelling some of those tribes. During that earlier period of conquest and integration, the construction and maintenance of roads was paramount: not only for military campaigns against the mountain tribes, but also during the wars against external neighbors.
Around the middle of the 19th century the situation changed. Russia began efficiently integrating most of her Caucasian possessions into the Empire and to pacify the remaining mountainous area. The first issue required further road construction and the extension of political, economic and social infrastructure. The second she achieved by changing military strategy, which also required military highways. For these ends Russia had to invest a great deal of men, money and time until she eventually could profit from the territory in a colonial sense. Thus she performed acts of a civilizing (Christian) mission, which had been the original motive for expansion and became a political and moral pretension for her. With the pacification and integration - and partly also the expulsion - of mountainous Muslim societies largely achieved in the second half of the 19th century, the search for additional passages over the Central Caucasus came to a gradual end while internal traffic was extended by stage-coaches and later by railroad construction.
The unremitting necessity of roads for warfare in a fragmented territory lacking infrastructure made for lines of transit which were named "military highways". Some of them served exclusively military ends. Although some have since lost their function, others, which were created, extended or improved by Russian engineers, kept their importance owing to their economic function. By the end of the 19th century the whole of the Caucasus acquired the traffic network as it exists still today in Transcaucasian space, which again is politically, socially and economically fragmented. This network stands as the great achievement of Russia's benevolent mission in the 19th century. With the few exceptions of ancient trade routes in the South Caucasus, i.e. parts of the Silk Road, at the start of the century there were hardly any modern.
Lastly the modernization of the Caucasus under Russian rule became a European story, in which a great number of non-Russian experts in Russian service took part, as engineers, administrators, scientists and politicians.