North Korea has started construction on a west coast island near Nampho, according to NK Pro analysis of satellite imagery, after leader Kim Jong Un ordered the navy to build modern bases for large new warships under development.

Planet Labs imagery shows the new activity started on Sok Island (석도) between July 15 and 25, with work consisting of clearing and improving roads and building temporary administrative or camp structures for workers.

More such structures appeared in two open patches of farmland on the southern coast of the island in the first half of August, along with construction of new paths through a forested hill in the southwest.

It’s too early to determine if the work is indeed related to Kim’s naval base plans, but historical imagery shows the activity is unusual and comes around the same time as the resumption of construction on a large naval base on the opposite coast.

It also follows Kim’s instructions to start building modern naval bases at a June commissioning ceremony for the country’s first 5,000-ton destroyer, the No. 51 Choe Hyon. He said at the time that the navy currently lacks a single base that can host new destroyers and larger planned ships.

NK Pro analysis of Planet Labs imagery shows the Choe Hyon destroyer remained at the location of the ceremony, a civilian cargo port in Nampho, as of Aug. 16, despite state media falsely suggesting it sailed away from the port to formally deploy for regular operations.

It’s unlikely the navy will choose a location for the base near the port or the Nampho Shipyard where the destroyer was built, since Nampho Bay is enclosed by the West Sea Barrage and its single lock-gate entry point — an easy target during a conflict that would leave the ship incapable of sailing out into the ocean.

Imagery does show preparations ramping up for large-scale construction at the Nampho Shipyard in recent weeks, but this is likely related to Kim’s orders to start building larger 10,000-ton warships.

Given the relatively shallow waters and extreme tidal range on the west coast, Sok Island appears to be one of the few suitable locations for a naval base capable of hosting large new ships.

The area of activity on the island is also right across the water from one of the largest existing naval bases on the west coast located at the Cape of Pipha.

One potential problem a naval base on Sok Island would face, however, is the tendency for the waters surrounding it to partially freeze in winter, likely hindering naval operations. This can last for almost two months during particularly severe winters, like from early January to early March 2018, or just a handful of days in milder years.

The waters around the larger Cho Island to the south, which already hosts a small naval base, have frozen less frequently since 2016, according to NK Pro analysis of Planet Labs historical imagery. 

Recent imagery shows no signs of upgrading facilities at Cho Island or at Pipha, however.

On the east coast, Planet Labs imagery shows that the No. 52 Kang Kon destroyer has remained stationed at Rason Port since June. 

NK Pro spotted the ship sailing south of the port on the morning of Aug. 12, just hours after North Korea conducted a missile test further down the coast — possibly in order to monitor some aspect of the test, or just as part of separate navigation trials.

Edited by David Choi