North Korea’s Kim Jong-un has just turned 40, but North Korea’s propaganda machine has said not a word about the fairly young leader’s birthday.

Instead, he’s ordered the war machine of his impoverished country, in what may have been a birthday celebration of sorts, to expend at least 300 artillery shells in three days in an exercise in muscle-flexing. 

While the North Korean state press publicizes Mr. Kim’s achievements and ambitions, Mr. Kim apparently fears his relatively young age may be held against him. The birthdays of his revered grandfather, the regime founder Kim Il-sung, who died in 1994, and his father, Kim Jong-il, who died in 2011, are national holidays. 

Rather, by ordering almost daily artillery barrages off the North’s western coast, Mr. Kim has been putting on a display that may be intended to impress Moscow as much as Washington and Seoul as he rules  out talks with either South Korea or America. 

The shells have fallen harmlessly into the sea, but South Korea now promises to test-fire some of its own artillery perilously close to the demilitarized zone that’s divided the Korean peninsula since the signing of the Korean War truce in July 1953. 

The decision effectively scraps a deal reached in 2018 under which North and South agreed not to stage exercises near the DMZ or the “Northern Limit Line” below which North Korean ships are banned in the Yellow Sea. 

South Korea’s Yonhap News reports the South “will resume artillery firing and drills near the sea and land border.” A military spokesman was quoted as saying “buffer zones that ban hostile acts no longer exist” as a result of North Korean artillery firing. 

That blunt assessment fits in with the general conservative position of South Korea’s President Yoon Suk-yeol, who has advocated a tough line against the North while enthusiastically approving joint exercises of American and South Korean troops. American forces were also expected to join the latest war games near the DMZ.

By test-firing the artillery, Mr. Kim appears anxious not only to intimidate South Korea, and possibly America and Japan, but also to convince Russia of the effectiveness of its munitions.

North Korea has shipped several million shells that Russia needs to pursue its war in Ukraine, but a number of them have been defective, and some have reportedly exploded accidentally.

So far the rounds of test-firing have been quite harmless, but South Korea, with memories of a North Korean artillery barrage that killed two South Korean marines and two workers on a small island off North Korea’s southwestern coast in November 2010, is taking no chances.

Seoul is urging residents of a string of islands in the Yellow Sea either to find shelter in or near their homes or to return to the mainland. 

The North Korean artillery testing comes on top of reports that North Korea is shipping missiles as well as shells and other armaments that the Russians are deploying in Ukraine.

Russia, in accordance with the understanding that Mr. Kim reached with Mr. Putin at the cosmodrome near the Amur River in September is providing technological assistance for North Korean spy satellites – and long-range missiles launched the same way.

“North Korea’s willingness to supply some of the weapons that Russia is using to kill Ukrainians fits a broader pattern of recent behavior by the Kim regime,” writes analyst Denny Roy in the National Interest.

“Pyongyang,” he added, “has stiffed US government attempts to re-open bilateral dialogue, declared that reunification with South Korea is impossible, and committed itself to never giving up its nuclear arsenal.” 

Instead, says Mr. Roy, a senior fellow at the East-West Center in Honolulu, Mr. Kim “has concluded that his interests are best served by closer association with China and Russia.”