When Russian forces first launched a North Korean missile at Ukraine, it landed in a field outside the southern city of Zaporizhzhia.

The United States said the attack had probably ended in abject failure.

Since then, Western analysts and the US have estimated that as many as 50 North Korean-produced short-range ballistic missiles have been used by Russia against Ukraine.

Those looking for clues on who gains what from Vladimir Putin’s trip to the hermit nation of North Korea could do worse than studying the battlefields of Ukraine.

While Putin is an obvious beneficiary of more weapons, Kim Jong-un is also gathering indispensable knowledge and intelligence on his own fledgling missile programme.

“North Korea has been able to test the efficacy of their small arms in various other conflicts around the world, but they haven’t been able to test their missiles anywhere,” Samuel Ramani, a fellow at the RUSI think tank, said.

Since North Korea started sending weapons to Russia, it has shipped at least 10,000 containers, Shin Won-sik, South Korea’s defence minister, said last week.

They have been stuffed full of 152-millimetre artillery shells, 122mm rockets, anti-tank missiles and portable surface-to-air missiles.

Putin has said the two countries’ relationship will be ramped up to a “new level” in a new partnership signed on Wednesday during his state visit to North Korea.

Their trade in missiles has been less well publicised.

But declassified US intelligence has directly linked fragments of rockets found in Ukraine to images of Kim touring a missile factory.