Van Dantzig was among the dancers who founded the Netherlands Dance Theater in 1959, but in 1960 he returned to Gaskell's company, by then named Nederlands Ballet. After this company and the Amsterdam Ballet merged to become Het Nationale Ballet (Dutch National Ballet), van Dantzig filled a number of important positions. He became resident choreographer in 1961, a member of the artistic council in 1965, co-director in 1968, and sole artistic director in 1971. He remained in that post for two decades, until 1991. He had a talent for administration and a keen eye for importing and commissioning ballets that expanded the company's repertory and developed its dancers.