As part of their plan to re-build Germany, the USA secretly released a new currency, the Deutsche Mark, printed in New York, to replace the old Reichsmark. Frustrated at how the US, UK and France were re-building their zones of Germany without first reaching an agreement with the USSR, on June 24 1948, Stalin erected a physical blockade (or, as he preferred to call it, “a defensive measure”) around West Berlin to prevent all traffic from Trizonia from entering into the city. The response of the US/UK was a massive airlift – an incredibly bold move, basically threatening Stalin to shoot their planes down and start another war. Luckily he chose not to do that, and instead backed down and ended the blockade. Meanwhile, Truman signed National Security Council document No. 30 (NSC-30) officially known as the “United States Policy on Atomic Warfare” – which made it official that the US would continue to use nuclear weapons as part of their arsenal.