(1) In the 18th and 19th centuries the term “line troops” was used in the armies of various countries to refer to the heavy (line) infantry, which operated in closed order and delivered the main strike, as distinguished from the light infantry, which operated in extended order and performed auxiliary missions. At that time the term “line” was also applied to heavy cavalry.
(2) Troops in the Russian Army who were chiefly involved in defending fortified border lines. Line troops appeared in 1804. By 1856 there were 84 line battalions—18 Georgian, 16 Black Sea, 13 Caucasian, 12 Finnish, ten Orenburg, and 15 Siberian units. With the exception of the Black Sea battalions they were all included in infantry brigades (five to seven battalions apiece); the Finnish, Orenburg, and Siberian units also had infantry divisions. In 1858 the Georgian and Black Sea battalions were renamed the Caucasian battalions, and in 1867 the Orenburg and some of the Siberian units were renamed the Turkestan battalions. By the beginning of the 20th century all the line forces had been reorganized as rifle and reserve troops. Between 1832 and 1860 there was a Caucasian Cossack Line Host.