As Russian President Vladimir Putin meets North Korean leader Kim Jong Un in Pyongyang, the ties between Russia and North Korea are the strongest they have been in decades.

Moscow and Pyongang announced a new defense pact on Wednesday, including "mutual assistance in case of aggression against one of the parties to this treaty," according to Putin.

The news follows reports of North Korea providing artillery shells, and — if US and Ukrainian sources are to be trusted — even ballistic missiles for Russia to use in Ukraine, with Russia allegedly offering assistance in military and satellite technology. Both sides denied these reports, at this would mean breaking the UN arms embargo against North Korea.

South Korea: Pyongyang could have delivered nearly 5 million shells

Last week, South Korea's Defense Minister Shin Wonsik said his country detected up to 10,000 shipping containers traveling from North Korea to Russia, which could contain up to 4.8 million artillery shells. In an interview with the US-based media corporation Bloomberg, Wosnik said Putin was likely to ask for more during his visit to Pyongyang.

An earlier report by US intelligence spoke of "at least 3 million" North Korean shells being delivered to Russia.

If confirmed, these deliveries would be a massive boon to Russia in its war of attrition in Ukraine, where both sides have complained of chronic "shell famine" hampering artillery strikes.

Talking to DW Russian, Austrian military expert Wolfgang Richter pointed out that Kyiv's EU allies had failed to provide even a million shells to Ukraine within the self-imposed deadline of one year.

"In the end, after a year, only about half of [a million] was delivered, with the rest to come by the end of this year," he said.

He also estimated that North Korea had likely provided up to 3 million artillery shots to Russia.

"It might not be decisive, but it is a significant supply," Richter said.

US, Ukraine say Russian forces use North Korean missiles

In January, the US accused Moscow of using short-range ballistic missiles supplied by North Korea to hit targets in Ukraine. The missiles fired by Russia have a range of about 550 miles (900 kilometers), according to US national security spokesperson John Kirby. He did not provide details on the types of missiles used, but a graphic distributed by the White House showed KN-23 and KN-25 short-range ballistic missiles (SRBMs).

Ukrainians later collaborated claims of North Korean rockets being used against them, saying they have examined remains of over 20 North Korean missiles fired on their territory. Last month, US Defense Intelligence Agency (DIA) declassified a report providing what they claimed was photo evidence on crashed North Korean rockets in Ukraine.

Pyongyang still locked into rivalry with Seoul

Military expert Richter says it is less clear if the North Koreans have indeed provided Russia with missiles, even though it was "possible to imagine" that some of their older missile systems ended up in Ukraine.

North Koreans are "especially interested in developing new, advanced systems and benefit from Russian missile technology," he told DW.

Pyongyang is also careful "not to completely deplete their stocks in favor of Russia … because they want to remain prepared for a conflict on the Korean Peninsula" Richter added, referring to current tensions in the region with South Korea, Japan, and the US.

"The Koreans, too, have to maintain balance, as their supply is also not infinite," he said.

Photo op in Pyongyang

With Russia also expanding its domestic military production, the exact impact of North Korean weapons is hard to quantify. However, Russian forces seem to have the initiative on the frontline and are slowly suppressing Ukrainian forces in recent months.

North Korea is also believed to be helping Moscow's war effort off the battlefield, with Pyongyang reportedly sending laborers to Russia and Russia-occupied areas to replace workers that have been conscripted to fight.

At the same time, the North Korean regime is also lending support on the diplomatic front. Since the beginning of the Ukraine war, North Korea has openly supported the invasion and become the third country in the world — after Russia and Syria — to recognize Ukraine's breakaway regions of Donetsk and Luhansk as independent nations in July 2022.

North Korean leader Kim Jong Un staged a massive welcome event for the Russian president Deutsche Welle

Pyongyang is also one of the few cities in the world still willing to stage a lavish photo op for Vladimir Putin — a symbolic but important weapon in Moscow's struggle to break out of its international isolation.

Moving towards Russia, away from China?

Now, Kim's loyalty to Putin seems to be paying off. Not only is Russia now committed to defending North Korea in case of an "aggression," it is also expected to provide energy and know-how to improve the country's economy and military arsenal. Pyongyang's military cooperation with Moscow is now arguably closer than with its traditional ally and protector, Beijing.

Analysts believe that Russia's support has already made Kim bolder, as he continues to escalate tensions with South Korea.

"We can clearly see a change in North Korea's behavior recently, becoming more aggressive," Hyun Seung-soo, an expert in North Korea-Russian relations at the Seoul-based Korea Institute for National Unification, told DW.

"I absolutely agree that Kim is more dangerous now because he is confident that he has a large and powerful friend in Russia," Hyun said. "He could see this as a chance to take military actions against the South. This recent rude behavior is very dangerous."

However, moving closer to Russia might cause Kim to lose ground in Beijing, according to Richter. China is worried that expanding Pyongyang's nuclear arsenal could provoke the US to increase its presence in the region.

"I'm not sure if China is really happy about this development," he said. "It seems they would then signal to Russia not to go too far, and not to break the non-proliferation regime."