O Britancima se može misliti ovo ili ono, ali uglavnom ne zaboravljaju svoje saveznike tako lako koliko možda i SAD. 1939. nakon što je napadnuta Poljska, Francuska se dugo nećkala oko objave rata, Britanci nisu.
Iako je ovo primarno bilo usmjereno protiv SSSR-a kao prijetnje za ostatak Europe, jedan od najvažnijih ciljeva, i motivacija bio je oslobođenje Poljske.
Planovi nisu bili oni "obični", kakvi se prave za svaki mogući hipotetski scenarij, nego izuzetno detaljni i razrađeni. Najkontroverzniji dio plana je bio korištenja čak 10 divizija Wehrmachta i SS-a. Na kraju ništa od svega jer nije bilo američke potpore.
Churchill ordered his joint planning staff to draw up the blueprint at the beginning of May in 1945, shortly after Hitler had committed suicide and the Red Army had captured Berlin.
The papers in the National Archives reveal how the aim of the plot was to impose on Russia the 'will of the United States and British Empire.'
Milton writes of the 'remarkable' level of detail in the plan. It included tables, charts and maps, along with tables listing the strength of both the Soviet and Allied forces.
From July 1,1945, Allied forces would launch a surprise attack on Stalin's forces, pushing the Red Army back to the Oder and Neisse rivers, 55 miles east of Berlin.
By this point, Soviet troops were occupying Berlin and had control of Eastern Europe, including Poland.
The Western assault, which would be the largest tank offensive in history with 8,000 armoured vehicles used, would end with a huge showdown in the countryside in Soviet-occupied Pila, in what is now north-west Poland.
Despite the significant difference in the number of Allied divisions when compared to their potential adversaries, Thompson outlined how naval superiority would be used to good effect – with a seizure early on of the Baltic port of Stettin.
Thompson hoped that stopping Western exports to Russia would cripple its military. Milton explains that the Soviet Union was dependent on America for explosives, as well as rubber, aluminium, copper and 50 per cent of its aviation fuel.
However, he warned that the Russian Army's 'capable' high command had a 'disregard for losses' when trying to obtain a 'set objective'.
He warned Churchill that, if they were to proceed, they would be 'staking everything' on one epic battle where the odds would be 'very heavy'.
It was for this reason that he proposed re-arming the Wehrmacht and the SS. Doing so would add another ten divisions, all of which would be made up of men hardened by six years of war.
Despite level of detail in the plan – and the time and effort which went into devising it - Churchill's military chiefs were horrified by it.
Field Marshal Sir Alan Brooke said Allied troops would end up 'committed to a protracted war against heavy odds'.
General Hastings Ismay was disgusted by the idea of using Hitler's defeated troops. He said it would be 'absolutely impossible for the leaders of democratic countries even to contemplate.'
He said the Russians had done the 'lion's share of the fighting and endured untold suffering'.
To attack them so soon after the end of the horrendous conflict would be 'catastrophic' for morale.
More than 27million Russians – both civilians and combatants – had died during the conflict, far more than Britain's casualty figure of around 450,000 and the US's 407,000.
Most historians agree that it was Russia's resistance to Nazi Germany's attempted invasion - leading Hitler to fight a war on two fronts - which sealed the country's defeat.
Field Marshal Brooke added that the chance of success of Operation Unthinkable was 'quite impossible'.
On June 8, Churchill's chiefs of staff officially rejected the plan.
However, the PM – who was to be turfed out of office a little over a month later in the 1945 General Election – was not happy with the death of the plan.
Milton outlines how Churchill told his Foreign Secretary Anthony Eden that if Stalin's territorial desires were not dealt a definitive blow 'before the US armies withdraw from Europe and the Western world folds up its war machines, there is very little prospect of preventing a Third World War.'
Churchill also warned his military chiefs that the Red Army would soon become impossible to beat.
He said: 'At any time that it took their fancy, they could march across the rest of Europe and drive us back into our island.'
The Operation Unthinkable file claims that the plan had the 'full support of public opinion in the British Empire and the United States' – a nod to general concern about the growing power of the Soviet Union.
Brigadier Thompson warned that the conflict might develop in a way which allowed Soviet troops to withdraw into Russia without suffering 'decisive defeat'.
If this were to happen, he added that there was 'virtually no limit to the distance to which it would be necessary for the Allies to penetrate into Russia in order to render further resistance impossible'.
Laying out the bleak outlook further, he said that even if it were to go according to plan', 'the military power of Russia will not be broken and it will be open to her to recommence the conflict at any time she sees fit'.
As for the US, President Harry Truman – who came to office after the death of Roosevelt in April 1945 – made it clear in a military cable that there was
no possibility that Americans would lead an effort to drive Russian troops from Poland by force.