Paul D. Hanson was an Army sergeant in his early 20s during the first of two tours of duty in Vietnam when his late-night poker game was interrupted by an attack on the firebase he was guarding.

Hanson, now 70 and living in Aston, said more than 1,000 enemy soldiers poured out of the jungle surrounding the firebase as mortar and rocket fire whizzed over the concertina wire.

He radioed for help, expecting artillery fire.

What he got was something powerfully different.

The USS New Jersey, to the east in the South China Sea, trained its 16-inch guns toward the source of Hanson's troubles.

"All of a sudden, the whole world exploded," Hanson told a crowd gathered on board the battleship New Jersey on Saturday for an event to honor Vietnam War veterans. "It came in over the top of us like a freight train."

The firepower was so stunning, Hanson said, that both sides stopped fighting for a moment and turned to look east.

The effect of that power was on display when the sun came up. An intersection outside the firebase where the enemy had been marshaling forces had become a 13-foot-deep crater littered with body parts.

Hanson and his comrades were able to resume their poker game. It worked out well for him.

"I always won money," Hanson said, laughing.

Hanson served 22 years in the Army, retiring as a sergeant major. He now supervises docents who guide tours on the battleship, permanently berthed on the Delaware River in Camden.

On Saturday, about 40 people in military garb, some veterans and some reenactors, displayed vintage uniforms, weapons, radios, and other gear in the battleship's wardroom as guest speakers told war stories.

The event started with the unveiling of a POW-MIA "chair of honor," an empty seat meant to remind visitors of service members who never come home.

Patrick J. Hughes, 68, of Glen Mills, organized the chair ceremony through Rolling Thunder, a nonprofit group that includes many military veterans and motorcycle riders.

Hughes was a 19-year-old lance corporal when the Marine Corps sent him to Vietnam in 1967. He worked on an air base and, in his free time, helped build an orphanage in a nearby village.

"In all honesty, I saw little or no combat," he said. "I shot at people I didn't see. I know I got shot at."

The "chair of honor" concept got its start at a Tennessee race-car track, spread to Massachusetts, and then across the county, Hughes said. His group also tries to draw attention to military personnel missing in active combat zones.

"The thing is, you don't leave anyone behind," said Hughes, wearing a tan vest covered with military patches and pins.

Jon Showers was on board the battleship in authentic Vietnam-era fatigues even though he was just 6 years old in 1968 when the war claimed the life of his stepfather. His father made it home from a tour of duty there.

Another relative received a Bronze Star for sacrificing his life to save his comrades in Vietnam.

Showers, 52, lives in Berks County and served six years in the Marines, including a tour in Beirut, Lebanon.

He started the Dogs of War, a group of Vietnam War reenactors, because he felt the conflict's history needed more attention.

"It's to educate the next generation about what happened in that era so we learn from our mistakes and don't repeat them," Showers said. "In war, everyone loses."