MUNSAN, South Korea, May 17 — Trains crossed the border between North and South Korea on Thursday for the first time in 56 years, an event both sides described as a milestone for reconciliation on the divided Korean Peninsula.

As white balloons soared into a blue sky, soldiers swung open gates topped with barbed wire shortly after noon to let the five cars of the South Korean train cross the 2.5-mile-wide demilitarized zone, the world’s most heavily armed border, and enter North Korea.

At the same time, about 144 miles east, a North Korean train trundled down the coast.

Although these were technically just one-time test runs on two short stretches of railroad that were linked through the demilitarized zone several years ago, their symbolic importance was unmistakable. The last trains that crossed the border carried refugees and wounded soldiers to South Korea from the North during the Korean War in 1951.

Photographs of the bullet-scarred, rusting hulks of wartime locomotives trapped in the demilitarized zone have symbolized a divided Korea and a conflict that has never been formally resolved, because the war ended in a truce, not a treaty.

“These are not just test runs,” said South Korea’s unification minister, Lee Jae-joung. “They mean reconnecting the severed bloodline of the Korean nation.” He spoke during a ceremony at Munsan Station, about seven miles south of the demilitarized zone. “The trains carry our dream of peace.”

His North Korean counterpart, Kwon Ho-ung, who was also in Munsan, said the trains represented the “Korean nation’s wish to gallop to the destination of reunification,” despite what he called outside forces — apparently a reference to the United States — that are “not happy with reconciliation among Koreans.”

The South Korean train, carrying 150 people from both sides of the border, pulled out of Munsan around 11:30 a.m. as fireworks exploded overhead. It traveled about 15 miles to Kaesong, a North Korean border town where South Korea runs factories employing less-costly labor from the North. The North Korean train had a similar journey, from the Mount Kumgang resort to Jejin, 15 miles to the south.

South Korea has long dreamed of building a trans-Korea railroad that would connect its trains to China and to the Trans-Siberian Railway. A route through North Korea would provide overland access to the rest of Asia.

A trans-Korea railroad would offer a faster and cheaper way for South Korea to send exports that are now shipped by sea to China and Europe. It would also provide a shortcut for Russian oil and other natural resources transported to South Korea. Such a rail system would save South Korea $34 to $50 a ton in shipping costs, said Lim Jae-kyung, a researcher at the Korea Transport Institute.

But creating such a system, transportation analysts and government officials say, would require years of confidence-building talks and billions of dollars in investment in North Korea’s decrepit rail system.

Officials acknowledge that North Korea will probably have to give up its nuclear weapons and improve its human rights record before it could attract significant investment from South Korea or international development aid. Six-nation talks aimed at ending North Korea’s nuclear weapons programs have been stalled for months.

“I cannot understand why we should give rice, flour, fertilizer and everything else the North Koreans want when they don’t do anything for us,” said Hong Moo-sun, 71, one of a dozen South Koreans protesting just outside Munsan Station on Thursday.

The protesters were calling for North Korea to return their relatives, among the hundreds of people taken to North Korea after the war and believed to be held there against their will.

Members of the Grand National Party, part of the conservative opposition, called the event on Thursday a “train of illusion” organized to draw voters’ attention in an election year.

South Korean officials say a trans-Korea railroad would invigorate inter-Korean trade, which tripled to $1.35 billion last year from $430 million in 2000. It would also bring cash to North Korea, which could collect an estimated $150 million a year in transit fees from trains that pass through its territory, Mr. Lim, the researcher, said.

But procuring international aid to renovate the rail network and letting trains from one of Asia’s most vibrant economies, carrying exports and tourists, rumble through its isolated territory could threaten the North Korean government, experts say. They say North Korea now relies on keeping its people ignorant of the outside world to maintain its totalitarian grip on power.

Both Koreas agreed in 2000 to reconnect their rail systems, which had been severed by aerial bombing during the war. It took three years to relink the tracks on the west and east ends of the border. After four more years of haggling and delays, the North Korean military agreed this month to allow the one-time test runs.

The agreement came after South Korea promised to send North Korea 400,000 tons of rice, as well as $80 million worth of raw materials for shoes, soap and textiles.

South Korea has spent $589 million on reconnecting the rail system, including $195 million worth of equipment, tracks and other material lent to North Korea.

South Korean policy makers have called for patience in working toward reconciliation with the North. They have often been accused by conservative politicians and civic groups of giving in to North Korea’s strategy of extracting economic aid for every step toward reconciliation.

“This is a precious first step for a 1,000-mile journey,” Mr. Lee, the unification minister, said Thursday.

WASHINGTON, May 17 — Paul D. Wolfowitz, ending a furor over favoritism that blew up into a global fight over American leadership, announced his resignation as president of the World Bank Thursday evening after the bank’s board accepted his claim that his mistakes at the bank were made in good faith.

The decision came four days after a special investigative committee of the bank concluded that he had violated his contract by breaking ethical and governing rules in arranging the generous pay and promotion package for Shaha Ali Riza, his companion, in 2005.

The resignation, effective June 30, brought a dramatic conclusion to two days of negotiations between Mr. Wolfowitz and the bank board after weeks of turmoil.

“He assured us that he acted ethically and in good faith in what he believed were the best interests of the institution, and we accept that,” said the board’s directors in a statement issued Thursday night. “We also accept that others involved acted ethically and in good faith.”

In the carefully negotiated statement, the bank board praised Mr. Wolfowitz for his two years of service, particularly for his work in arranging debt relief and pressing for more assistance to poor countries, especially in Africa. They also cited Mr. Wolfowitz’s work in combating corruption, his signature issue.

Mr. Wolfowitz said he was grateful for the directors’ decision and, referring to the bank’s mission of helping the world’s poor, added: “Now it is necessary to find a way to move forward. To do that I have concluded that it is in the best interests of those whom this institution serves for that mission to be carried forward under new leadership.”

Mr. Wolfowitz’s negotiated departure averted what threatened to become a bitter rupture between the United States and its economic partners at an institution established after World War II. The World Bank channels $22 billion in loans and grants a year to poor countries.

But he left behind a place that must heal its divisions and overhaul a flawed, cumbersome structure that had allowed the controversy over Mr. Wolfowitz to spread out of control.

People close to the negotiations said that Mr. Wolfowitz had agreed not to make major personnel or policy decisions between now and June 30. Some bank officials said he might go on an administrative leave and cede day-to-day functions to an acting leader, but that might not be decided until Friday.

President Bush earlier in the day praised Mr. Wolfowitz at a news conference but signaled that the end was near by saying he regretted “that it’s come to this.” A White House spokesman, Tony Fratto, said, “We would have preferred that he stay at the bank, but the president reluctantly accepts his decision.”

More important for the bank’s future, Mr. Fratto said, President Bush will soon announce a candidate to succeed Mr. Wolfowitz, quashing speculation that the United States would end the custom, in effect since the 1940s, of the American president picking the bank president.

Many European officials previously indicated that they would go along with the United States’ picking a successor if Mr. Wolfowitz would resign voluntarily, as he now has.

Treasury Secretary Henry M. Paulson Jr. said Thursday that he would “consult my colleagues around the world” before recommending a choice to Mr. Bush, in what seemed to be an effort to assure allies that the United States would not repeat what happened in 2005 when Mr. Bush surprised them by selecting Mr. Wolfowitz, then a deputy secretary of defense and an architect of the Iraq war.

Leaders of Germany and France objected but decided not to make a fight over the choice and risk reopening wounds from their opposition to the war two years earlier. Some also argued that Mr. Wolfowitz, as a conservative seeking to write a new chapter in a career that had been focused on national security, might bring new support to aiding the world’s poor.

Soon after Mr. Wolfowitz took office, however, he engaged in fights in various quarters at the bank over issues including his campaign against corruption, in which he suspended aid to several countries without consulting board members, and his reliance on a small group of aides.

Mr. Wolfowitz’s resignation, while ending the turmoil that erupted in early April over the disclosure of his role in arranging Ms. Riza’s pay and promotion package, will not by itself repair the divisions at the bank over his leadership, bank officials said Thursday evening.

By all accounts, the terms of Mr. Wolfowitz’s exoneration left a bitter taste with most of the 24 board members, who represent major donor countries, as well as clusters of smaller donor and recipient countries. Most had wanted to adopt the findings of the special board committee that determined he had acted unethically on the matter of Ms. Riza.

But the closest the board came to criticizing Mr. Wolfowitz was saying in that “a number of mistakes were made by a number of individuals in handling the matter under consideration and that the bank’s systems did not prove robust to the strain under which they were placed.”

Also angered was the bank’s staff association, which had called for Mr. Wolfowitz’s resignation in early April. The bank’s internal blogs were filled with denunciations of the action on Thursday evening.

Late in the evening, the association issued a statement saying, “Welcome though it is, the president’s resignation is not acceptable under the present arrangement,” and that it “completely undermines the principles of good governance and the principles that the staff fight to uphold.”

The association represents most of the 7,000 full-time employees at the bank in Washington. Their unhappiness could be a crucial factor in the bank board’s ability to heal the wounds left by the fight over Mr. Wolfowitz. It appeared likely that after Mr. Wolfowitz’s departure there would be a departure of several top aides, including Robin Cleveland, who officials said was involved in the negotiations over the statements accompanying his departure.

During the day, as word spread throughout the institution that Mr. Wolfowitz was close to a deal, some officials said that one of the obstacles was his compensation package. But there was no information Thursday night on whether he would receive any sort of severance package or pension, or be reimbursed for legal fees from his long battle.

Mr. Wolfowitz’s pay package was $302,470 in salary as of 2004 — the bank pays any of the taxes on that sum — and $141,290 in expenses. His contract calls for him to be paid a year’s salary if he is terminated, but it was unclear whether his resignation would be considered a termination as defined by the contract.

Mr. Wolfowitz’s fight for vindication was led by his lawyer, Robert S. Bennett, and negotiated at the bank by the British director, Thomas Scholar, a close associate of Gordon Brown, the chancellor of the Exchequer who is to become prime minister this summer.