Every day, South Korea's Unification Ministry sends officials to the border village of Panmunjom to call North Korea at 9 a.m. and 4 p.m. For more than 18 months, the North hasn't picked up.

As North Korea steps up its nuclear weapons tests and threats, the Unification Ministry faces an almost existential crisis.

It wasn't too long ago that the ministry was one of Seoul's most powerful departments. It had central roles in engineering two historic summits between the leaders of the two Koreas and launching joint economic projects in the 2000s. That is mostly gone after nearly a decade of hard-line conservative rule in the South, and a rapid expansion of missile and nuclear weapons development in the North.