That was a sequel. The original game was Invasion: America, which was about North America (the United States, allied Canada, and occupied Mexico) being invaded by an alliance of the European Socialist Coalition, the Pan Asiatic League, and the South American Union. The game was released in 1976 and was a big success so they followed it up in 1978 with Objective: Moscow, in which the Cold War went the other way and it was the Soviet Union being invaded.
Sixth Column was probably also inspired by the earlier German invasion genre which was popular in Britain before WWI. This genre started with The Battle of Dorking and ran through The Riddle of the Sands.
Invasion literature has been common since at least 1871. There were a lot of British novels about how Germany was going to invade the U.K. The American novels about the Soviets invading were relatively late on the scene:
[spoiler]By the skin of their teeth. IIRC (it’s been 10 years since I last read it), the US forces had stopped the Soviets cold in the south, and the only breakthrough was in the north, between the British and Germans. There was a huge American counterattack north to cut off the breakout, and at that point, the Germans (I think) sued for peace.
The book was more of a cautionary tale to try and illustrate the way the Soviet doctrine was supposed to have worked, along with some interesting and human characters. (I was pretty fond of the artillery Colonel who liked to garden, myself)
[/spoiler]
Soviet film about Sherlock Holmes highly appreciated Queen of England - she said it was the best film about Holmes and presented the award.
As a Sherlock Holmes fan, I must politely ask for a cite.
[Yakov Smirnov/]: In Soviet Russia, film appreciate YOU!
Sherlock Holmes: