Prince Alexander meant invaders from the west - the Swedes, whom he defeated in 1240, and the Teutonic knights, against whom he fought the great battle on the ice of the river Neva - hence his title - in 1242. Eisenstein's film was made as a warning and as preparation for impending war against Germany. But that scene provided a neat summary of a very Russian preoccupation: the fear of encirclement, and of war against two enemies - or three, or four - at once.
That recurring fear has resurfaced as the Russian bear puts up a steel- shod paw against Nato enlargement. When so encircled, Russia always rates the West as its most formidable opponent.
In October, the former national security adviser Alexander Lebed met General Klaus Naumann, the Chairman of Nato's Military Committee, and told him Russia had security concerns in three areas. The first was the West, by which he meant Nato, and potential Nato members - especially Poland - and Ukraine, which has no intention of joining Nato. The second was the south-west - the Middle East, and the third was the south - Iran and Afghanistan. He did not mention China specifically, but the East has been a frequent concern and may become one again. And - bearing in mind that any strategic attack by the United States, with bombers or missiles, could come over the North Pole - Russia feels surrounded.
The country's darkest hours were in the Middle Ages and in 1918-20. In the 13th century the Russian principalities were attacked by Danes, Swedes, Poles, Germans and Hungarians from the west and by Mongols from the east. After the Russian revolution of 1917, the area controlled by the Bolshevik government shrank to much the same area as the medieval principality of Muscovy. Germans occupied Ukraine: the British, French and Americans attacked in the north; and the British also in the south, where the anti- revolutionary White Guards wereconcentrated, and the Japanese landed in the Far East. These attacks were uncoordinated, inept, and soon pushed back.
The memory of these comparatively recent foreign interventions is raw, and relevant, to modern Russians. Most relevant of all is the surprise attack by Germany - until 22 June 1941 a formal ally of the Soviet Union - which, in six months, overran an area equivalent to that conquered by Alexander the Great. Anyone who doubts that relevance should remember the Russian response when it was proposed to put Russian officers in Nato headquarters as a confidence-building measure. "We had officers in the Wehrmacht headquarters in 1941," said a Russian colonel. "Look where that got us."
At its greatest extent, the Russian or Soviet Empire occupied about a sixth of the earth's land surface. Until 1867, the Russian empire traversed three continents and went more than half way round the world - Alaska, sold to the US for a song, was Russian. Russia itself still covers one eighth of the land surface of the world. It also has about 12,000 nuclear warheads.
Why should such a countryfeel encircled? Since the Soviet break-up, Russian intellectuals have resurrected Sir Halford Mackinder's idea of the "heartland", and the historian's famous proposition that control of eastern Europe was crucial to control of the heartland. Furthermore, "those who rule the Heartland dominate the World Island [Eurasia]; those who rule the World Island dominate the world". But that very central position makes Russia vulnerable to isolation by oceanic powers who want to seize the rim of the world island.
Russia's traditional response to encirclement has been to divide potential enemies, and to push them further away. The main force behind the development of the Soviet navy from the 1960s seems to have been that having pushed the "enemy" as far away as it could on land, the Soviets then had to push it further still. As a large part of the "threat" came from US aircraft carriers and US, British and French ballistic-missile firing submarines, they wanted to push that further away, too.
Madeleine Albright, the new US Secretary of State, is trying to reassure the Russians that Nato enlargement is not a threat. Given the history of the past 750 years, she has a hard task ahead.