Russia's full-scale war against Ukraine could last another four to six months and become a frozen conflict similar to the Korean War.

James Stavridis, former commander-in-chief of NATO forces in Europe, said this in a commentary to Business Insider.

According to the military officer, the Ukrainian army is putting up strong resistance to the Russian occupiers, and Russian President Vladimir Putin's plans proved "not particularly effective."

He noted that Putin has gained little territory in Ukraine "compared to what he started the conflict for". 

"I see this leading to the end of the 'Korean War,' that is, an armistice, a militarized zone between the two sides, continued hostility, a kind of frozen conflict. We will see this within four to six months. Neither side can hold out much longer than that," Stavridis said.