<P> The Soviet Union was the other ally of the Viet Minh, supplying GAZ trucks, truck engines, fuel, tires, arms (thousands of Skoda light machine guns), all kind of ammunitions, anti-aircraft guns (4 x 37 mm type) and cigarettes . During Operation Hirondelle, the French Union paratroopers captured and destroyed tons of Soviet supplies in the Ky Lua area . According to General Giap, the Viet Minh used 400 GAZ - 51 soviet - built trucks at the battle of Dien Bien Phu . Because the trucks were using highly effective camouflage, the French Union reconnaissance planes were not able to notice them . On May 6, 1954, during the siege, Katyusha were successfully used against the outpost . Together with China, the Soviet Union sent 2,000 military advisors to train the Viet Minh and turn it into a fully organized army . </P> <P> At the beginning of the war, the U.S. was neutral in the conflict because of opposition to European colonialism, because the Viet Minh had recently been their allies, and because most of its attention was focused on Europe where Winston Churchill argued an Iron Curtain had fallen . </P> <P> Then the U.S. government gradually began supporting the French in their war effort, primarily through the Mutual Defense Assistance Act, as a means of stabilizing the French Fourth Republic in which the French Communist Party was a significant political force . A dramatic shift occurred in American policy after the victory of Mao Zedong's Communist Party of China in the Chinese Civil War . By 1949, however, the United States became concerned about the spread of communism in Asia, particularly following the end of the Chinese Civil War, and began to strongly support the French as the two countries were bound by the Cold War Mutual Defense Programme . </P> <P> After the Moch--Marshall meeting of September 23, 1950, in Washington, the United States started to support the French Union effort politically, logistically and financially . Officially, US involvement did not include use of armed force . However, recently it has been discovered that undercover (CAT)--or not--US Air Force pilots flew to support the French during Operation Castor in November 1953 . Two US pilots were killed in action during the siege at Dien Bien Phu the following year . These facts were declassified and made public more than 50 years after the events, in 2005 during the Légion d'honneur award ceremony by the French ambassador in Washington . </P>

Why did the united states support the french war effort in vietnam