(CN) --- The war in Ukraine intensified on Sunday as fierce fighting was reported across the country and Russia made more progress in its brutal campaign to strangle its southwestern neighbor and bring Kyiv back under Moscow's control.
Sunday saw the invasion become even more of a danger to escalate into a broader conflict as Russian President Vladimir Putin put his military on nuclear alert and showed no sign of backing down from his wild plot to take control of Ukraine in defiance of international condemnation and even risk war with the West.
Although Ukrainians were putting up stiff resistance, it appeared that Russian troops were making advances in attacking Kyiv, the capital of 3 million inhabitants, and encircling Ukrainian forces in the eastern part of the country as Russian troops pushed up from Crimea and the south toward the Donbas, where a war has simmered for the past eight years between pro-Russian separatists and Ukrainian forces, according to an analysis by the Institute for the Study of War.
On Saturday, there was hope that Russia's invasion was failing, fueled in part by images of civilians taking up arms and videos of burning Russian tanks and armored vehicles. But military experts say the likelihood is that Russia will seize the country. It is believed that about 50,000 of the 150,000 troops Russia parked at the borders of Ukraine in advance of the invasion have been deployed.
“I think it's a bit early to draw conclusions about the success or otherwise of the Russian campaign,” said Chris Deverell, a former British commander who helped lead the 2003 invasion of Iraq, speaking on Sky News television.
“It's possible that the Russians have some logistic issues, and it is likely that the Ukrainians are fighting back hard, but I also think that at some point it's likely that the Russians will take control of Kyiv, but not without a fight.”
He said the Russians will avoid trying to take cities because they don't want to get bogged down in street fighting. With Ukrainians showing great determination to fight, he said he expected the war to become “very bloody” when Russia tries to seize cities.
“The evidence is that Putin's life depends on making Ukraine into a clan state, so he's all in,” he said. “So at the end of the day, I don't think he's going to restrict his use of weaponry or tactics to achieve his aim.”
Sunday saw both sides accusing the other of war crimes, the shelling of civilians and extreme violence. Huge toxic fumes billowed out of oil depots struck in Kyiv, presumably by Russian missiles, and in Donetsk, an industrial city in eastern Ukraine where pro-Russian Ukrainian rebels are based.
Russian and Ukrainian diplomats were tentatively expected to meet to negotiate a possible ceasefire at a site on the border with Belarus, though reportedly the talks had not started as of Sunday night.
Still, the prospects of a ceasefire are highly uncertain and the expectation is that the war is set to only become bloodier as Russian troops advance on Kyiv. Many in Ukraine are keen to keep up the fight and the West is talking about supporting a sustained insurgency against a Russian occupation.
“If [Putin] succeeds in his ultimate objective, which is regime change, and force Zelenskyy out of power, arrest him or kill him, we need to continue to support the resistance,” said Michael McFaul, a former U.S. ambassador to Russia, on NBC's Meet the Press on Sunday.
Such an insurgency would be reminiscent of a bloody guerilla war that anti-communist Ukrainians waged at the end of World War II against Joseph Stalin's totalitarian rule. That insurgency failed and Stalin shipped hundreds of thousands of Ukrainians into the gulag system.