 Complete the following phrase:  Nà Sản Airport was built in 1950 by the French as part of their army outpost in Nà Sản. Initially, the airport had a short clay airstrip but it was then extended and paved with pierced steel planking to be able to handle larger planes like the Douglas DC-3. In October 1952, the outpost was fortified to create a hedgehog defense against the Viet Minh forces in what was to become the 