Organizers named it the National World War II Reunion, so 82-year-old Ray "Ace" Acevedo arrived prepared to reunite with anyone he could find from the Army's 15th Air Force.

Like hundreds of veterans at the opening of the four-day exposition on the Mall yesterday, Acevedo tacked his phone number onto a bulletin board in the "Reunion Hall" tent. If he was lucky, he thought, maybe someone from his 460th Bomb Group would give him a call.

"I don't even know how many of those guys are still alive," said Acevedo, of Goleta, Calif.

Another veteran walked to the bulletin board about the same time, and they got to talking. He also served with the 460th in Italy. They discovered they had left the country at the same time, by the same route, maybe even on the same plane. Acevedo found the man's picture in a photo book he'd brought from home. They reminisced about bombing runs, and the coffee and doughnuts waiting for them upon return. Some of the memories caught Acevedo by surprise -- he hadn't envisioned some of those details in decades.

"It's amazing how many things come back to you," he said.

His experience illustrated the overriding goal of the weekend's full schedule of World War II-themed events: to spark the memories of veterans, get them talking and allow others to listen, celebrate and learn. The National Park Service estimates that as many as 800,000 people will visit the Mall throughout the holiday weekend, with the largest attendance expected tomorrow when the National World War II Memorial is dedicated.

The first of the large crowds converged on the Mall yesterday morning with the opening of the Reunion exposition, which continues from 11 a.m. to 7 p.m. through Sunday. The event was organized by the Smithsonian Institution and the American Battle Monuments Commission.

In anticipation of the dedication, several hundred people lined up throughout the day for last-chance tickets to the ceremony. Organizers had announced earlier in the week that they would begin distributing any returned tickets at 11 a.m. yesterday. The line on the Mall began to form well before that, though officials had made no guarantees that any tickets would be available.

"We got here at midnight, but it took us a couple hours to figure out where the tickets were going to be given out," said Gregory Newman, 57, a Vietnam veteran who spent the night on a nearby park bench talking with his friend Yomi King, also 57 and from the District. "The next person in line came around 6 a.m., then the line started filling in around 7."

The sixth person in line was Philip Rush, 84, who stood there from about 6:30 to 11:30 a.m. for three tickets for himself and his two daughters. A Navy veteran of World War II, the Arlington resident said that even though he was a charter member of the drive to build the memorial, he didn't learn how to get tickets to the ceremony until this spring, after all tickets had been spoken for. Like several other veterans in line, he said waiting for a few hours seemed worth it, considering they had waited 60 years for a memorial.

By the end of the day, organizers had distributed all 1,300 returned tickets. They reminded those wishing to attend the 2 p.m. dedication that the event will be simulcast on large screens set up throughout the Mall and that viewing areas will be available for those without tickets. Some of those areas have first-come, first-served seating, while others are standing-room only.

The Mall sounded and looked more like 1944 than 2004 in many places yesterday. On the outdoor "Homecoming Stage," the singing group the Ink Spots, which formed in 1932 with different members, sang such standards as "When the Saints Come Marching In" and "We'll Meet Again." Inside the "Capitol Canteen" tent, the USO Liberty Belles boogie-woogied, while at the "Wartime Stories" tent, former U.S. senators and presidential candidates Bob Dole and George S. McGovern swapped tales of their war experiences.

At the "Motor Pool," people milled around what in the 1940s amounted to state-of-the-art military transport vehicles: a fleet of Willys jeeps, a camouflaged 1941 Plymouth staff car, a 1943 Indian motorcycle, a 1944 GMC "Duck" amphibious vehicle. And inside the "Family Activities" tent, a group of eighth-graders from Norwood (N.J.) Public School -- 17 girls and, eventually, six reluctant boys -- learned some basic swing dance steps.

Throughout the Mall, a small army of 400 volunteers from the Library of Congress approached veterans and asked to hear their stories. The volunteers audiotaped the conversations for the Veterans History Project, an effort to collect and preserve veterans' wartime memories. Thousands of hours of interviews are expected to be sorted and organized throughout the summer, and project coordinators said they hoped to have many of the interviews available online in about six months at www.loc.gov/vets.

But it wasn't only archivists and volunteers who were eager to listen to stories; many of the attendees said they hoped to stroll around and solicit memories firsthand from their elders.

"I was in first grade when the war ended," said Arnold Pawlowski, 65, of the District. "I'm just looking forward to listening to stories from all of these old men. We owe them so much, and thank God they're still with us."

Navy veteran Richard Sargent, 78, of Springfield, who served in the Pacific, looks for the names of friends on a message board at the "Reunion Hall" tent.Several hundred people, some arriving at midnight Wednesday, line up for last-chance tickets to the memorial dedication.Edward Foley, 87, from Berwick, Pa., who served with the 455th Bomb Group in the Pacific, meets with other 455th members, Raymond Acevedo, 82, left, and Howard Cooper, 79.