OTL : Soviets blockade Berlin in 1948.
OTL : Allies launch Operation Plainfare to keep the city supplied as in OTL.
ATL : Soviets forcibly close the air corridors in early 1949, downing planes and attacking the three airports (2 in the UK occupation zone, 1 in the US) where the planes take off.
ATL : Soviet forces rumble forward towards the Rhine.
OTL : In 1948, there's no NATO, no joint command, and the US had largely demobilized its troops in Europe. Germany has not rearmed, France is recovering from WW2 and is tied up in Indochina.
ATL : In a matter of weeks, the Soviet forces are in full control of Germany, France, Greece and the Lower Countries. Half of Switzerland is invaded. Italy, rocked by Communist-inspired strikes, declares itself neutral and welcomes PCI members into the government.
ATL : The USSR demands bases in Norway and Sweden, as well as right for troops, ships and planes to pass through these nations's territory. Both nations refuse.
ATL : Soviet forces move into Sweden via Finland, which nevertheless remains a non-belligerent.
ATL : The UK is not invaded, but revives the 1940 Blitz. Its most modern divisions that were part of the British Army on the Rhine have been destroyed.
ATL : recently re-elected Harry Truman's popularity tanks, as he becomes the man who lost China and Europe the same year. Europe is seen as a lost cause for the time being, and in 1949 Congress forces the US administration to give the priority to reinforce Japan where large US forces light face an incoming invasion.
OTL : North Korea moves South, crushing the ill-prepared ROK troops.
ATL : All plans for offensive operations in Europe are shelved until further notice. The US deploys fighters to help the UK defend itself, and de-mothballs planes and ships to be used to keep supplies going to the British.
ATL : Japan is allowed to rearm in 1950 so as to relieve the pressure on the US in terms of costs and manpower. Truman gives the green light to the use of atomic weapons against DPRK/Chinese PLA units. The 5th fleet conducts deep raids and coastal bombardment runs along the Chinese coastline.
ATL : With neither CHina nor the USSR having any interest in containing the Korean War, this conflict drags on at least until 1957, and ends up with a statu quo as China and the USSR start having irreconcilable ideological differences. China takes the lead in the management of the Korean War, and accepts a return to the statu quo ante that makes the DPRK a Chinese puppet. Formosa is retaken by the PLA, after Mao accepts to let the KMT forces evacuate to Japan.
ATL : The US starts drafting up plans for operations in Europe starting 1959.
At least from 1948-1959, the Soviet Union is triumphant, and in true Stalin/Molotov fashion can use its dominant position to force concessions by Persia and Turkey.