Complex sentence: The United Kingdom was one of the victors of the Second World War, but the cost of the war was massive, national savings were exhausted, and the late 1940s were a time of austerity and economic restraint, that gave way to prosperity in the 1950s.
Split into simpler sentences: The United Kingdom was one of the victors of the Second World War, but the cost of the war was massive, and the nation's realisable assets were exhausted. Thus the late 1940s were a time of austerity and economic restraint, which gave way to prosperity in the 1950s.