Criminal investigators armed with a court warrant prepared a second, long-awaited operation early Wednesday to detain President Yoon Suk Yeol for questioning on sedition charges stemming from his brief imposition of martial law last month.

Police buses started gathering before dawn in front of the presidential compound on top of the hill where Mr. Yoon has been in hiding since the National Assembly impeached him – and suspended him from office – on December 14. He was the first South Korean leader to place his country under military rule since the country began to democratize in the late 1980s.

When investigators first visited his residence to serve him with an arrest warrant on January 3, they were outnumbered by presidential security agents. They were met by barricades of cars, bodyguards and soldiers and had to endure an uncomfortable retreat after a five and a half hour standoff.

On Wednesday morning, with Mr. Yoon’s lawyers, lawmakers from his party and personnel from the presidential security service standing outside the entrance to the compound, he and his supporters appeared to be preparing to resist renewed efforts to detain him.

Investigators have regrouped since their first failed attempt to detain Mr. Yoon, they renewed their warrant and said they would bring more police officers the next time they visited his residence. Police officials said they plan to deploy 1,000 officers, including units specializing in the fight against drug gangs and organized crime.

On their part, security guards Mr. The Yoonas have since fortified the compound by deploying multiple buses and razor wire to block the doors and walls. Mr. Yoon has vowed to “fight to the end” to return to office and said he will not surrender to a court order he considers illegal.

The attempt to detain Mr. Yoon is the first time in South Korea’s history that the authorities have attempted to detain a sitting president. The unfolding events swept the country, with news and social media channels broadcasting live. There are fears of violent conflict if neither side backs down.

A day earlier, the Constitutional Court started a debate on whether Mr. Yoon, who didn’t show up. His lawyers said he feared investigators would catch him if he left his presidential compound.

During the latest attempt to serve the warrant, the Presidential Security Service, the government agency tasked with protecting the president and his family, outnumbered the Corruption Perceptions Office (CIO), which attempted to arrest him with the help of the police. He hired 200 bodyguards and soldiers to block 100 CIO agents and policemen.

It was not clear how many men the presidential security team might muster in a new attempt to arrest Mr. Yoon.

A military unit guards the perimeter of the presidential complex. But after the initial standoff, the Defense Department told the presidential security service it could no longer use soldiers to block the serving of warrants, saying it was not part of the soldiers’ duties.