The ruling Workers' Party of the Democratic People's Republic of Korea, is preparing to hold its first congress in 36 years, starting on May 6. The event is expected to showcase the recent advances in the DPRK's nuclear weapon and missile programs. In South Korea, hardliners and advocates of diplomacy remain divided over how to respond. 

It’s been year so far in the DPRK. A fourth-nuclear bomb test, the launch of a satellite on a rocket capable of doubling as long-range missile, multiple shorter-range missile tests, including from a submarine, and claims of miniaturizing a nuclear bomb to fit in a warhead.

"After Kim Jong-un came to power their nuclear capability rapidly advanced and switched from developing an atomic bomb to a hydrogen bomb," Cheong Seong-Chang, director of Unification Strategy Studies Program, said.

"They got the results from the first three tests, from the fourth test the focus was how to increase the power and make a strategic weapon," Lee Choongeun, research fellow tih Science and Technology Policy Institute, said.

Smaller and more powerful nuclear weapons are being developed in tandem with the DPRK’s accelerated missile program.

Pyongyang’s stated aim is to miniaturize a nuclear device small enough to fit on the tip of an intercontinental missile capable of reaching as far afield as the United States.

Some advisers to the South Korean government believe the DPRK already has medium-range nuclear missile capability.

"It's not difficult for the DPRK to miniaturize the bomb for the No-dong missile. But the ICBM has to endure a greater degree of heat and they don’t have the sort of technology to reach that level yet,"  Lee said.

South Korea is considering deploying a controversial U.S. anti-missile system. Though some still hope talks with Pyongyang could be restarted.

"To make them stop an advanced nuclear missile America and the DPRK need to reach a settlement. If they stop the test the U.S. and South Korea must reduce the United Nations training and the DPRK would need to freeze operations at its Yongbyong nuclear facility,"  Cheong said.

Tough sanctions introduced by countries including China aim to slow the development of an effective long-range nuclear weapon. But many experts say without renewed diplomatic efforts that program can only be slowed, not brought to an end.