North Korea has showcased what appears to be significant progress in constructing a nuclear-powered submarine, releasing images of a largely completed hull as leader Kim Jong Un lashed out at rival South Korea's parallel efforts to acquire the technology.
A Strategic Naval Milestone
According to a report from state media on Thursday, 25 December 2025, Kim Jong Un inspected the vessel at an undisclosed shipyard. The official Korean Central News Agency (KCNA) described it as an 8,700-ton-class nuclear-propelled submarine, a project Kim has previously labelled crucial for modernising and nuclear-arming the nation's navy.
The regime intends to arm the submarine with nuclear weapons, referring to it as a "strategic guided missile submarine" or a "strategic nuclear attack submarine." During the visit, Kim condemned South Korea's push for its own nuclear-powered submarine—a move backed by U.S. President Donald Trump—as an "offensive act" violating the North's security and maritime sovereignty.
Analysing the Revealed Images
The newly released photographs, the first since March, show Kim inspecting a huge, burgundy-coloured vessel coated in anti-corrosion paint inside an assembly hall. He was accompanied by senior officials and his daughter. Submarine expert Moon Keun-sik of Hanyang University noted that because submarines are built from the inside out, a largely complete hull suggests core components like the engine and possibly the reactor are already installed.
"Showing the entire vessel now seems to indicate that most of the equipment has already been installed and it is just about ready to be launched into the water," said Moon, a former South Korean navy submarine officer. He believes sea trials could commence within months.
Regional Arms Race and Global Concerns
The development is part of a sophisticated weapons wish list Kim announced in 2021, which also included solid-fuel ICBMs and hypersonic weapons. A functional nuclear-powered submarine would grant North Korea a harder-to-detect, second-strike capability, significantly altering the strategic balance on the Korean Peninsula.
Questions persist over how the sanctioned, impoverished state obtained the necessary resources and technology. Some analysts point to North Korea's deepening alignment with Russia, including military support for the war in Ukraine, as a potential source of technical assistance. While some suspect a reactor from a retired Russian submarine, Moon believes it is more likely North Korea designed its own with possible Russian help.
Tensions continue to escalate. In a separate report, KCNA stated Kim supervised a test of a new long-range anti-air missile fired toward the East Sea on Wednesday. These moves come as diplomacy remains stalled, with Pyongyang dismissing calls from Washington and Seoul to revive denuclearisation talks.
