South Korea joined an exclusive club last week, becoming only the eighth country to successfully test-fire a submarine-launched ballistic missile (SLBM), as its rival to the north stepped up preparations for a military parade that could see Pyongyang unveil yet more powerful weapons.

Seoul test-launched what is believed to be a variant of the Hyunmoo-2B ballistic missile, which has a roughly 500-kilometer range, from its 3,000-ton Dosan Ahn Chang-ho submarine last week, the South’s Yonhap news agency reported Tuesday.

The successful launch means South Korea has joined seven other countries — all nuclear-weapon states — in possessing the technology. The United States, China, Russia, France, India, the U.K. and North Korea arm their SLBMs with nuclear warheads, or are believed to do so.