Avoid the August Coup. If it never happened, the New Union Treaty would be signed. The USSR has at least a chance to survive (albeit smaller and with many of OTL Russia's problems).
Yeah. This was the latest you can save the USSR if you don't want economic reforms in the 1960s. The 9 republics who voted yes wanted to, in fact 75%+ of the people who participated were in favor of retaining the Union!
Perhaps later on Gorbachev allows other parties in power, but not those which favor secession from the Union.
The USSR shall survive, it'll recover much faster than any post-Soviet scenario, as there will be no breakdown in trade between the respective republics and Gorbachev's going to be in power, therefore no Boris Yeltsin and co. ultra-liberal catastrophe IOTL. By 2000, they would have recovered to 1988 levels, and if they enact more reforms, maybe the second largest economy on Earth, maybe even on par with the USA by 2016.
I was in the Army under Carter. He was no friend to the Armed Services. Had the USSR jumped us on his watch we would have folded like a house of cards due to shear lack of ordinance. Remember how the Iranianians gave our Embassy folks back within minutes of Reagan taking over after flipping Carter the bird for over a year.The military was hollowed out from Vietnam as it crowded out spending. The military was actually recovering by the end of Carter's tenure.
You do realize Carter graduated in the top 10% of his class from the US Naval Academy and spent 7 years in the navy including a few tours on a submarine?
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Not to mention that your idiotic scenario violates Soviet nuclear doctrine as well: .....................