When the units got back from the war, they went their separate ways.

For more than 50 years, the four Japanese-American units from the Islands — whose members were fighting a nation's enemies in World War II along with the monster of discrimination at home — never united formally to commemorate the lives of their comrades lost on the battlefield. Then, three years ago, the planning began.

"All of the veteran groups were depleting in members," said Robert Arakaki, president of the 100th Battalion Veterans Association. "We knew what needed to be done. ... It took us a very long time to organize this joint memorial. During that time, we organized a fine connection."

The first-of-its-kind memorial is set for 9 a.m. Sunday at the National Memorial Cemetery of the Pacific at Punchbowl. Presidents of the veterans' associations for the four units, along with an estimated 700 veterans, family members and dignitaries, will attend.

For the near future, three of the four Japanese-American units have pledged to host the memorial. This year, the 100th Battalion paid for the costs of the gathering and wreaths for the memorial. Next year, the 442nd is expected to take them on, followed by the Military Intelligence Service.

In the 100th Battalion headquarters on Kamoku Street on a recent afternoon, which is quiet but for the hum of a television and low chatting in the lounge, Arakaki goes over last-minute details for the memorial.

He gets teary-eyed when he talks about his fellow soldiers who died in the war — and who have died since. Slowly, he says, the unit is disappearing. At 83, he's one of the youngest left.

Thomas Takemoto, president of the 1399th Battalion, agreed it was important the four units gather before their ranks shrink any more. "Every year, boys are passing away," he said. "My time is coming, too."

Veterans from the units have different answers as to why the memorial wasn't held sooner. Ron Oba, president of the 442nd, said it was because each unit had its own interests and "did our own things."

Also, for decades there was an awkward tension between the 100th and the 442nd, whose members received more fanfare and press coverage after the war. The 100th Battalion went into battle first, and its members came back in small groups — many from hospitals — while the war was still raging. The 442nd came back en masse when the fighting was over.

"The 442 came back with color, they had a parade," Arakaki said. "When the 100th came back, they came back as individuals."

But Arakaki says members of the two units were always good friends and never held a grudge. "In due time," he added, "you get old enough to understand you need each other." Meanwhile, vets of the 1399th and the Military Intelligence Service got even less public praise after the war.

On O'ahu during the war, members of the 1399th built 54 military installations, including jungle training grounds for soldiers.

The Military Intelligence Service was made up of Nisei who translated documents and interrogated Japanese prisoners of war — all under a cloak of secrecy. The extent of their service during the war was not known until recently, when members started to talk about their experiences.

Amanda Stevens, office manager for the 100th Battalion, said in planning the memorial she has come to realize just how much was at stake for the 19- and 20-year-old Japanese-Americans from the Islands who joined the Army to fight in the war. "They've done so much for minorities," she said, "not just for Japanese."