The 'Mozhaysk Defence Line' was a Soviet defence line protecting Moscow from attack by Generalfeldmarschall Fedor von Bock’s Heeresgruppe 'Mitte' moving along the primary axis from Smolensk to Moscow (July/30 October 1941).

The Soviet dictator, Iosif Stalin, decreed the creation of the line on 18 July under the command of General Leytenant Pavel A. Artemev. The line was constructed between the Volga Reservoir in the north and the upper reaches of the Upa river in the south via Volokolamsk, Mozhaysk, Maloyaroslavets and Kaluga.

The outermost Soviet line in front of Moscow had been the 'Vyaz’ma Defence Line' extending along an essentially north/south axis between a point to the east of Lake Seliger and a point to the north-west of Bryansk via a central point on the Moscow Highway to the west of Vyaz’ma. This was shielded by General Major Vasili A. Yushkevich’s (from 20 October General Major Vladimir I. Vostrukhov’s) 22^nd Army, General Leytenant Ivan I. Maslennikov’s 29^th Army, General Major Vasili A. Khomenko’s 30^th Army, General Leytenant Ivan S. Konev’s (from 12 September General Leytenant Mikhail F. Lukin’s) 19^th Army, General Leytenant Konstantin K. Rokossovsky’s 16^th Army, General Leytenant Filipp A. Ershakov’s 20^th Army, General Leytenant Stepan A. Kalinin’s 24^th Army and General Major Mikhail I. Potapov’s 43^rd Army of Marshal Sovetskogo Soyuza Semyon K. Timoshenko’s (from 12 September General Polkovnik Konev’s) West Front against the advance of Generaloberst Walter Model’s 9^th Army, Generaloberst Hermann Hoth’s 3^rd Panzergruppe, Generalfeldmarschall Günther von Kluge’s 4^th Army and Generaloberst Erich Hoepner’s 4^th Panzergruppe of von Bock’s Heeresgruppe 'Mitte'.

From 2 October these German forces had driven forward from positions just to the east of Smolensk, and within five days their two Panzergruppen had punched through the 'Vyaz’ma Defence Line' in a pincer movement whose armoured elements met at Vyaz’ma, trapping vast numbers of Soviet troops and huge amounts of matériel in the Vyaz’ma pocket. The pocket had been destroyed by 14 October, the Germans taking something in the order of 650,000 prisoners. This phase of the fighting cost the Soviets at least 45 divisions.

With the German spearheads now less than 125 miles (200 km) from the Soviet capital, there was a general panic in Moscow, resulting in a huge exodus on 16 October with refugees blocking the roads as they streamed back. In the capital itself, although Stalin and the highest levels of the administration and armed forces remained, many departments of government and the diplomatic corps were ordered to move to the city of Kuybyshev deeper in the interior. A large number of officials and their families also joined in the flight. Looting was widespread, and on 19 October a state of siege was declared.

On 5/6 October Stalin had telephoned Leningrad to order the return of General Georgi K. Zhukov, who was co-ordinating the defensive preparations of the city. Zhukov returned by air to Moscow on 7 October, and discovered that communications with the West Front and Marshal Sovetskogo Soyuza Semyon K. Budyonny’s Reserve Front had largely broken down, preventing Stalin from obtaining information on the course of events.

Zhukov left to try to establish contact with the three fronts. That night he found Konev’s headquarters without much difficulty and heard the details of the Vyaz’ma encirclement. The Bryansk Front had put up uneven resistance, and nothing was known of Budyonny. Having telephoned Stalin in the early hours of the morning of 8 October, Zhukov set off in search of Budyonny, who was believed to be somewhere near Maloyaroslavets. After much difficulty, Zhukov came upon the headquarters of the Reserve Front, which knew little about the position of its own troops or of those of the Germans, or even the current location of Budyonny, whom it feared lost with Potapov’s 43^rd Army.

From Konev nothing had been heard for two days. Zhukov left the headquarters giving orders for the gathering and re-forming of detachments and stragglers, and set off in continued search of Budyonny.

There was never any question of undertaking the relief of the troops encircled in the great Vyaz’ma pocket as there were no forces available for the purpose, and it was decided to put every formation or detachment which could be mustered into the 'Mozhaysk Defence Line', which was a series of positions intermediate between the broken 'Vyaz’ma Defence Line' and the three concentric defence lines close round Moscow itself. The 'Mozhaysk Defence Line' was occupied by no more than 14 infantry divisions, 16 tank brigades and 40 rifle regiments, totalling some 90,000 men. This defence force began to concentrate on 14 October under the headquarters of Rokossovsky’s 16^th Army, General Major Konstantin D. Golubev’s 43^rd Army, General Leytenant Ivan G. Zakharkin’s 49^th Army and General Major Dmitri D. Lelyushenko’s (later General Major Leonid A. Govorov’s) newly formed 5^th Army, all of which were regrouping in the 'Mozhaysk Defence Line', where General Major Semyon I. Bogdanov was supervising the preparation and co-ordination of the fortifications.

More armies were already being drawn into the area, however. Some thinning of the troop formations in the Far East began at about this time, and General Leytenant Pavel A. Kurochkin’s North-West Front and Marshal Sovetskogo Soyuza Semyon K. Timoshenko’s South-West Front transferred some of their formations to the Moscow area.

On 10 October Zhukov assumed command first of the Reserve Front and then of the West Front, the two fronts being fused into one command. Konev, the former commander of West Front, became Zhukov’s deputy commander. Konev was not to remain long in this post, however, because of a new crisis which had arisen to the north-west of Moscow, where the 3^rd Panzergruppe, now commanded by Generaloberst Hans-Georg Reinhardt, was moving to the north-east, entering Kalinin on 14 October in the rear of the 22^nd, 29^th and 31^st Armies, which fell back in disarray. This led to the creation on 17 October of a new Kalinin Front under Konev with Vostrukhov’s 22^nd Army, Maslennikov’s 29^th Army and Khomenko’s 30^th Army as well as an operational group under General Leytenant Nikolai F. Vatutin. The new front extended at right angles to West Front from Kalinin in the east to the Ostashkov Lakes in the west.

Zhukov was made responsible for the defence of all of the approaches to Moscow and commanded all troops on the defence lines. Artemeyev, commander of the Moscow Military District, was entrusted with the defence of the city under Zhukov’s overall control.

On 18 October the armour of General Georg Stumme’s XL Corps (mot.) had already entered Mozhaysk on the second defence line about 60 miles (95 km) from Moscow, after some fierce fighting against three tank brigades near Borodino, and the 'Mozhaysk Defence Line' had already been breached by General Adolf Kuntzen’s LVII Corps near Maloyaroslavets and Borovsk, and by General Walter Schroth’s XII Corps near Kaluga.

There was also a threat to the Naro-Fominsk and Podolsk areas to the south of Moscow, and there also existed the possibility of the communications between Moscow and Tula being cut by the advance of Generaloberst Maximilian Reichsfreiherr von Weichs’s 2^nd Army.

To meet this situation a new formation, General Leytenant Mikhail G. Efremov’s 33^rd Army, was created in this area and the 43^rd Army was also reinforced. The three Moscow defence rings were strengthened by barricades, strongpoints and anti-tank obstacles, and three workers' divisions were hurriedly formed from volunteers and conscripted civilians. Thus was the position set for the launch of the German 'Taifun' (i) attempt to take Moscow.