An observer expects Moscow to focus more on holding cities "hostage" as its invasion collapses.

Prime Minister Justin Trudeau and other NATO leaders are scheduled to meet in an extraordinary meeting in Brussels on Thursday as experts warn that the war in Ukraine is likely to become bloodier as it enters a new and decisive phase.

The meeting will be held exactly one month after Russia's invasion of its neighbor in an attempt to overthrow President Volodymyr Zelensky's government.

The Russian military campaign stalled without taking control of the Ukrainian capital Kyiv or other major cities. Many military analysts say Moscow was relying on a quick victory and no longer has the new troops and equipment it will need to make significant gains now.

Meanwhile, Matthew Schmidt, an assistant professor and national security expert at the University of New Haven in Connecticut, said the Russian military strategy is evolving into a long-term conflict and will focus on "holding civilians and entire cities hostage" to force the Ukrainian government to surrender.

Oleksandr Danyliuk, former Ukrainian national security chief, agreed with this assessment and said Moscow's strategy moving forward will be to try to destroy the cities and people of Ukraine.

Danyliuk said, "The Russians realize they had no chance to win this war using the basic strategy and changed it to bombing Ukrainians, bombing Ukrainian cities, and killing as many innocent civilians as possible." 

Meanwhile, Trudeau spoke by phone with Zelensky about the rising number of civilian casualties before leaving for Europe on Tuesday.

The United Nations High Commissioner for Human Rights office earlier this week estimated that 902 civilians have been killed and 1,459 others injured so far due to the war.

On the other hand, Western intelligence agencies have begun warning that Belarus, Russia's ally, is preparing to enter the war with its forces. U.S. President Joe Biden indicated that Moscow could escalate the conflict using chemical weapons.

Danyliuk said both scenarios are highly likely. He estimated that Belarus has "days" before taking military action to support Russian President Vladimir Putin's stalled invasion.

 He added: "Putin will one day use chemical or nuclear weapons." "There is no other way [to win]. And we will not surrender despite this prospect."

Meanwhile, NATO, led by the United States, said it will not send ground troops to Ukraine but will continue to assist Zelensky's government.

Schmidt said the challenge facing NATO leaders in the coming days is to come up with new and innovative ways to counter Russia's strategy of slaughtering civilians.

He said the allies establishing a "humanitarian sea corridor" in besieged Mariupol—a southern coastal city where tens of thousands of civilians are trapped under continuous shelling with no electricity or water—would be risky but possible.

Schmidt added that Western forces could enter to evacuate civilians after issuing a notice that they would not get directly involved in the conflict or fire their weapons unless fired upon. He said it would be a calculated risk, achievable because of the weakness of Putin's army.

He added: "(Putin) now knows that his army is largely incompetent, even against the Ukrainians." "We are likely to be able to neutralize our threat."

“Allies still find it hard to stand by and watch so much suffering.”

Meanwhile, Danyliuk said his country needs more and better weapons and that NATO leaders need to find new ways to increase financial pressure on Russia and support the Ukrainian economy.

He said: "We need weapons and we need money." "Financial support for Ukraine is needed because this is not only a military issue, but also a big problem for the Ukrainian economy."

He added, "We will be effective in destroying Russian forces anyway."