KYIV, Ukraine >> The North Korean soldiers fighting for Moscow in Russia’s Kursk region are assigned their own patches of land to assault. Unlike their Russian counterparts, they advance with almost no armored vehicles in support.

When they attack, they do not pause to regroup or retreat, as the Russians often do when they start taking heavy losses, Ukrainian soldiers and U.S. officials say. Instead, they move under heavy fire across fields strewed with mines and will send in a wave of 40 or more troops.

If they seize a position, they do not try to secure it. They leave that to Russian reinforcements, while they drop back and prepare for another assault.

They have also developed singular tactics and habits. When combating a drone, the North Koreans send out one soldier as a lure so others can shoot it down. If they are gravely wounded, they have been instructed to detonate a grenade to avoid being captured alive, holding it under the neck with one hand on the pin as Ukrainian soldiers approach.

Sent to Russia to join with Moscow’s troops in Kursk, the North Koreans essentially operate as a separate fighting force, the Ukrainian soldiers and U.S. officials said — distinct in language, training and military culture.

“It’s partly two different militaries that have never trained or operated together and partly, I think, Russian military culture, which is, shall we say, not highly respectful of the abilities and norms and operations of partner forces,” said Celeste A. Wallander, who until Inauguration Day was the Pentagon’s assistant secretary for international security affairs.

The North Koreans are largely special operations troops trained for surgical strike missions, she said, but the Russians have basically used them as foot soldiers.

Last fall, North Korea sent about 11,000 soldiers to aid Moscow’s forces in the Kursk region of southern Russia, where the Ukrainians captured territory with a surprise invasion last summer. Since their first combat engagement in early December, roughly one-third of the North Korean soldiers have been killed or wounded, Ukrainian and U.S. officials said.

With 1.2 million troops, North Korea’s military ranks among the world’s largest standing armies, and its entry into the war was a profound escalation in a war now approaching its fourth year.

Even before it sent troops to Russia, North Korea was a major supporter of Russia’s war effort. It has sent Moscow millions of artillery shells — which now account for about half of the Russian munitions fired daily — and more than 100 short-range ballistic missiles, according to Western and Ukrainian intelligence officials.

The Kremlin has denied deploying North Korean soldiers to the battlefield and is taking steps to hide their involvement, officials said.

Ukrainian claims about attempts to hide North Korean participation could not be independently verified.