The 'Stalin Line' was a Soviet defence line in the western USSR extending along the full length of the long Soviet frontier with its western neighbours, running from a northern extremity at Narva on the Gulf of Finland to a southern terminus just to the west of Odessa on the Black Sea (22 June/1 September 1941).

From Narva the line ran to the south along the length of the Velikaya river via the eastern side of Lake Peipus, and then cut across from Idritsa to Polotsk on the upper reaches of the Dvina river before leaving this river at Vitebsk to extend to the south-east to Orsha on the Dniepr river. The line then followed the southward run of the Dniepr via Mogilev and Rechitsa to a point to the south of the Pripyet Marshes where the Dniepr river meets the Pripyet river. The line then swung to the south-west across agrarian Ukraine to reach the Dniestr river just east of Kamenets-Podolsky, and completed its run to the Black Sea down the Dniestr river.

The line had been constructed between 1929 and 1935 (and thus well before the westward extension of the USSR’s frontiers at the expense of the Baltic states and Poland) to protect the USSR’s current boundaries. The defences were not continuous, but rather a belt of defensive fire points, spaced some 1.25 miles (2 km) apart, together with artillery emplacements strengthened to resist heavy artillery fire.

After the USSR’s westward expansion of 1939/40 into the Baltic states and eastern Poland, the system was run down, and stripped of its weapons and garrisons, but immediately before the German 'Barbarossa' invasion of June 1941 Premier Iosif Stalin ordered the reactivation of this line and of the special defensive sectors in Karelia and at Polotsk, Korosten and Kiev.

By 9 July, less than three weeks after the start of 'Barbarossa', the Germans had closed up to the 'Stalin Line' along most of its length, the most notable exceptions being the sector behind the Pripyet Marshes, where General Leytenant Fyedor I. Kuznetsov’s 21^st Army of General Dmitri G. Pavlov’s West Front (ex-Western Special Military District) and General Leytenant Mikhail I. Potapov’s 5^th Army of General Mikhail P. Kirponos’s South-West Front (ex-Kiev Special Military District) were checking Generalfeldmarschall Walter von Reichenau’s 6^th Army and Generaloberst Heinz Guderian’s 2^nd Panzergruppe of Generalfeldmarschall Gerd von Rundstedt’s Heeresgruppe 'Süd' and Generalfeldmarschall Fedor von Bock’s Heeresgruppe 'Mitte' respectively, and the sector on the lower reaches of the Dniestr river, where General Leytenant Andrei K. Smirnov’s 18^th Army and General Major Matvei V. Zakharov’s 9^th Army of the South-West Front were holding back Generaloberst Eugen Ritter von Schobert’s 11^th Army and General de corp de armatâ Nicolae Ciupercă's Romanian 4^th Army of Heeresgruppe 'Süd'.

To balance these failures, the Germans had by this same date secured two significant breakthroughs, one in the north around Vitebsk (in the sector of Heeresgruppe 'Mitte') by Generaloberst Hermann Hoth’s 3^rd Panzergruppe, and one in the south around Zhitomir (in the sector of Heeresgruppe 'Süd') by Generaloberst Ewald von Kleist’s 1^st Panzergruppe. Very soon after this the German forces punched through the largely ineffective 'Stalin Line' along its whole length.