Somewhat peripheral to your main thesis, I could not resist writing an essay on some points you raised about Kaliningrad...

"it was selected as a forward position to eliminate Prussia as a consideration in the future. It wasn't intended to be defensible from the West."

Respectfully disagree with both points.

Germany attacked the USSR. As part of the postwar reduction of Germany Stalin had to take part of Germany for the USSR itself and not just for a satellite like Poland. If you look at a map of Germany on the eve of WW2 the obvious candidate was their isolated province of East Prussia. Stalin divided East Prussia into a gift for to Poland and a gift of the region around Königsberg for the USSR.

One key consideration was that Königsberg was formerly part of Russia. It had become a part of the Russian Empire in the large gains of territory as Empress Elizabeth's armies were crushing Frederick the Great's armies and were poised to annihilate Prussia. Immanuel Kant, the most famous resident of Königsberg, famously swore loyalty to Catherine the Great, Empress of Russia.

Unfortunately for Russia, Empress Elizabeth's psychologically deranged nephew, Peter III, was an idiot who was born in Germany, barely spoke Russian, was a fanatic admirer of Frederick the Great and, famously, put the interests of Prussia ahead of those of Russia. When Elizabeth died and Peter III took power as the only possible heir from the Romanov dynasty (his mother was the eldest daughter of Peter the Great and had been sent to Germany to marry a German duke), his first act as Tsar was to stop the war against Frederick and to give back all of Russia's gains, including Königsberg, to Frederick.

Peter III's reversals of huge military gains by Russia at the cost of many lives plus his treasonous elevation of Prussia from a state about to be destroyed into a European superpower was one of the reasons he was hated as a traitor throughout Russia, overthrown by his own wife, Catherine the Great, and later killed.

Peter III's gift of Königsberg to Frederick became a famous symbol of his treason that for nearly two centures rankled the Russian state as a crime that should be reversed. Stalin taking it for the USSR was very popular just for that reason.

By the way, if you search for the history of Königsberg on Internet most sources don't mention that it was ever part of the Russian empire, that Immanuel Kant willingly became a Russian citizen, or the bizarre circumstances of how Peter III gave it to his idol Frederick the Great.

Other reasons for taking Königsberg was that it was a better port on the Baltic Sea than St. Pete, the region was full of useful factories, wharfs and Prussian craftsmen that would help the USSR rebuild after the devastation wrought by the nazis, and that it had many outstanding seaside mansions in resort towns that appealed to the Communist leadership for use as dachas, in settings where they could kick back and enjoy their victory without any anti-proletariat vibes that would attach to their appropriation of Tsarist mansions in St. Pete.

As for not being defensible from the West, the opposite was true: Kaliningrad was superbly defended from the West because it was very deep inside Soviet-controlled territory, with the large Soviet vassal states of Poland and East German between Kaliningrad and Western Europe. On the other side Kaliningrad also had massive buffers in the form of Soviet-controlled Baltic state vassals, Russia itself, and a neutered Finland.

Unlike the softer leaders who followed Stalin, Stalin had no intention of loosening his grip on the buffer zone architecture that he had constructed to protect the USSR from attacks from the West.

That wasn't paranoia, either, as Stalin's intelligence services had thoroughly penetrated the US military: Stalin had every detail of Truman's plans to launch a nuclear first strike on the USSR while the US still had a nuclear monopoly. As early as December 1945 the US planned on a nuclear first strike to destroy the USSR in a sneak attack using 20 to 30 nukes on 20 cities, which rapidly grew by June 1946 to a plan using 50 nukes, followed up with conventional bombardments and invasion using ground forces, including a large West Germany army made up of WW2 Wehrmacht units that had survived in the West. As you can imagine, Stalin and the Soviet leadership were not happy to learn their former "ally" secretly planned to destroy the USSR.

Those plans to nuke the USSR in a sneak attack carried various names as they evolved, but the best known name is for an early 1949 plan, "Operation Dropshot" for using 300 nukes in a first strike. Dropshot is often sold in the West as a "contingency plan" to counter a Soviet invasion of the West, but in reality it is yet another sneak attack plan to wipe out population and cities across the USSR, not a response to a Soviet military invasion of the West.

Before any of Truman's plans could be implemented, the USSR surprised the US by testing an atomic device in 1949 much sooner than expected. But the series of first strike plans continued to be evolved as the US tried find a way to eliminate the USSR despite the USSR's rapidly increasing deterrent arsenal.

Almost nobody in the US knows that the Cold War and resultant nuclear arms race was started by Truman's plan to nuke the USSR with a sneak attack while the US still held a nuclear monopoly. Until those plans were declassified as a result of Freedom of Information Act requests and published in a now out-of-print book in 1987 ["To Win A Nuclear War: The Pentagon’s Secret War Plans" by Michio Kaku and Daniel Axelrod] nobody outside the nuclear war establishment knew about them.

If anybody wants to learn more about those plans, today it's hard to find truthful information on Dropshot and its predecessors in the West given the 24/7 propaganda narrative that now distorts Western sources.

For example, Wikipedia's description of Dropshot says: "Although the scenario included the use of nuclear weapons, they were not expected to play a decisive role" but then in the very next paragraph it mentions that the plan "would have used 300 nuclear bombs and 29,000 high-explosive bombs on 200 targets in 100 cities and towns to wipe out 85 percent of the Soviet Union's industrial potential at a single stroke." - as if the use of 300 nukes would not be "decisive" against a country without any nuclear weapons (the plan was created before the US learned the USSR had nukes - it was designed to be used before the USSR became a nuclear power, which the US thought would take many years).

The best option to learn more is to find a download of the 1987 book or buy one of the rare and expensive used copies that pop up every now and then online. The book's non-profit publishers, South End Press, disdained copyrights and went out of business years ago leaving many rights issues hanging, so the book appears to be in the public domain.

The lead author, Michio Kaku, has morphed from a progressive author into a solidly mercantile talking head for US propaganda media. It looks like he'd prefer to put as much space as possible between his current persona and such a politically incorrect book. Can't blame him given today's geopolitics.