The lost Marines of Tarawa still are missing.

A recent expedition to a tiny South Pacific atoll where a fierce World War II battle was fought -- conducted in part using the research of a Morgan Hill man -- did not uncover remains of U.S. servicemen.

But the Joint POW/MIA Accounting Command (JPAC) is planning to return before the end of the year, and this time the agency has invited Bill Niven to accompany the mission to ensure that searchers excavate precisely where he believes Marines were buried nearly 70 years ago.

"The key is they need to dig exactly where I tell them to dig," Niven said. "It's frustrating because I don't think they did that this last time out there."

This trip further underscores the difficulty of locating long-lost remains on the small, densely populated island of Betio where, in November of 1943, about 1,110 Americans died in a 76-hour battle against Japanese forces. JPAC, which is in charge of accounting for the more than 83,000 service members listed as missing since World War II, now has searched for the 560 unaccounted-for Marines five times since 2009.

"We're all disappointed that we didn't find any remains," said Johnie Webb, JPAC's deputy to the commander for external relations and legislative affairs. "But we're still optimistic that Bill has good information, and we're going to continue to search in the areas that he has suggested."

Niven, who was profiled by this newspaper in August, is a veteran of the Marine Corps Reserve and former airline pilot who has been studying the Tarawa battlefield for more than 20 years. Niven believes he has identified four unmarked burial sites with 98 Marines on Betio, an island in what was then known as the Tarawa atoll and today is part of the Republic of Kiribati.

JPAC workers scoured the island, located 2,500 miles southwest of Hawaii, in September, and Niven said he was under the impression that the focus would be on two locations he had identified, containing what he claims are 73 Marines -- including a Medal of Honor recipient.

But the search was wide-ranging, using not only Niven's information, but that of a Florida-based group called History Flight and the National Geospatial-Intelligence Agency. Niven said he's not convinced the team excavated where he had directed, or if they looked diligently enough.

"I'm frustrated because they're still not looking at my sites," he added.

It appears JPAC may agree. Niven said he has been asked to conduct a seminar for JPAC's "diggers" at the agency's Hawaii-based headquarters and also to go Tarawa on the upcoming expedition, perhaps in November.

Webb said this last mission was hurried because of the then-impending partial federal government shutdown. The team had to be back in Hawaii before the Oct. 1 shutdown deadline. That only added to the challenges of finding buried servicemen who died in one of the most well-known engagements in Marine Corps history.          

Sprawled bodies on the beach of Tarawa atoll testify to the ferocity of the battle for this stretch of sand during the U.S. invasion of the Gilbert
Sprawled bodies on the beach of Tarawa atoll testify to the ferocity of the battle for this stretch of sand during the U.S. invasion of the Gilbert Islands, in late November 1943. (ASSOCIATED PRESS)

"The complexity of trying to recover Marines and Navy personnel lost on Tarawa is amazing," Webb said. "There are just so many unanswered questions. Some of them never reached shore and might have been lost at sea. The geography has changed and now you now have a huge population on a small piece of ground. And then you have decades of activity and locals maybe finding remains and then disposing of them."

Niven, a history buff who has based his research on archival materials and old photographs of the battlefield, said he is not opposed to accompanying the next search. But he is concerned about being away from his two small businesses for an extended period of time.

Still, he added, "We need to be finding those kids."

JPAC has been under intense political scrutiny in recent months for not doing a better job of locating missing servicemen around the world. Finding Marines on Tarawa would go a long way to easing some of that pressure.

"It's important for people to know that while we might not have recovered remains this time, we're not going to give up," Webb said. "Bill is not going to give up. And we're going to keep working to bring those Marines home."

Follow Mark Emmons at Twitter.com/markedwinemmons.