CHICAGO (NewsNation) — A former top military official joined NewsNation’s “Rush Hour” Thursday to discuss the latest developments in Russia’s invasion of Ukraine, including when he believes the two sides will cease fire.

It looks like this war is going to go on for quite a while,” said retired Marine Col. Mark Cancian Thursday on NewsNation’s “Rush Hour”

Cancian is also a senior adviser at the Center for Strategic & International Studies. His prediction on how long the conflict between Russia and Ukraine will last is based on, as he put it, “both sides digging in.” But, more importantly, it’s because he feels there isn’t any overlap in the two countries’ respective positions on how the war might end.

“The Ukrainians are, quite reasonably, demanding that the Russians at least return to the lines on Feb. 23. The Russians don’t look like they’re willing to give up any of the territory they’ve occupied. There are no ongoing negotiations. So the war could go on for months, perhaps even years,” Cancian said.

This comes as Russia has pulled back its forces from a Black Sea island where they have faced relentless Ukrainian attacks.

The Kremlin portrayed the pullout from Snake Island as a “goodwill gesture.” But Ukraine’s military claimed it forced the Russians to flee in two small speedboats following a barrage of Ukrainian artillery and missile strikes. The exact number of troops was not disclosed.

Cancian says this is a great thing for Ukraine on two counts.

“First, it’s strategically important because it’s 28 miles off the Romanian coast on the west side of the Black Sea. That had been one of the ways (Russia has) been blockading Ukrainian ports preventing grain,” he said.

“But,” he added, “the other thing is, it says something about what the Ukrainians can do with their military forces. They’ve been hammering the island ever since the Russians took it over at the beginning of the war. They sank several Russia logistic ships and I think as a result, the Russians decided they just couldn’t hang on to it.”