Putin sees Ukraine as part of his "destiny" to "recreate the Russian Empire," said ex-Defense Secretary Gates.
"He is obsessed with retaking Ukraine. He will hang in there," Gates said on Sunday on NBC News.
The US and other military allies are sending tanks to Ukraine to aid the country against Russia's advances.
Russian President Vladimir Putin believes it's his "destiny" to recreate the Russian Empire, according to former US Defense Secretary Robert Gates.
During a Sunday interview on NBC's "Meet the Press," Gates said that Putin had made it part of his vision to retake old territories to recreate Russia's former geographic sphere of influence.
"Putin believes it's his destiny to recreate the Russian Empire. And as my old mentor, Zbig Brzezinski, used to say, 'Without Ukraine, there can be no Russian Empire,'" Gates said. "So he is obsessed with retaking Ukraine. He will hang in there."
"I think that he does believe that time is on his side, that support in the US, support in Europe, and so on, will fray. And he's doing what Russian armies have always done, and that is sending large numbers of relatively poorly equipped, poorly trained conscripts to the frontlines, in the belief that mass will overcome," he added.
Ukraine will soon receive a set of critical tanks from military allies - including the United States and the United Kingdom - in the country's continued efforts in warding off Russian forces.
Russia launched its invasion of Ukraine last February, and in the coming weeks, it will mark a full year since the beginning of the conflict.