I doubt that he will be able to close down the war in 24 hours, as he had promised. I rather think that he will escalate it. As I stated two weeks ago:

I expect the new president to double down on the anti-Russian project in Ukraine …

A new Wall Street Journal piece on Trump's promise does not give me any reason to believe otherwise.

Trump Promised to End the War in Ukraine. Now He Must Decide How. (archived
Foreign-policy advisers close to the president-elect put forth different versions of a plan to effectively freeze the front line

Like in Trump's first term, different factions are set to compete to influence the Republican's foreign policy. More traditionally minded allies such as Mike Pompeo, the former secretary of state now in contention to lead the Pentagon, are likely to push for a settlement that doesn't appear to give a major win to Moscow. Other advisers, particularly Richard Grenell, a top candidate to lead the State Department or serve as national-security adviser, could give priority to Trump's desire to end the war as soon as possible, even if it means forcing Kyiv into significant concessions.

But what are ways to do that?

One idea proposed inside Trump's transition office, detailed by three people close to the president-elect and not previously reported, would involve Kyiv promising not to join NATO for at least 20 years. In exchange, the U.S. would continue to pump Ukraine full of weapons to deter a future Russian attack.Under that plan, the front line would essentially lock in place and both sides would agree to an 800-mile demilitarized zone. Who would police that territory remains unclear, but one adviser said the peacekeeping force wouldn't involve American troops, nor come from a U.S.-funded international body, such as the United Nations.

"We can do training and other support but the barrel of the gun is going to be European," a member of Trump's team said. "We are not sending American men and women to uphold peace in Ukraine. And we are not paying for it. Get the Poles, Germans, British and French to do it."