Following four lengthy meetings spanning the past three months, Princeton’s Regional Planning Board last Thursday approved the Institute for Advanced Study’s proposal to build faculty housing on land it owns bordering the historic Princeton Battlefield. The Board voted unanimously for the plan, which was amended with modifications suggested at a previous meeting by historians James McPherson and David Hackett Fischer.

But Bruce Afran, attorney for the Princeton Battlefield Society, which vigorously opposes the plan, said the organization will appeal the decision. “The Planning Board was really just the opening skirmish,” he said Tuesday morning. “The main fight to preserve it is only just starting.”

Mr. Afran said he is preparing to challenge the Institute in light of a 1992 settlement agreement in which they gave up the right to build on the land bordering the Battlefield. In addition, he will ask the Department of Environmental Protection to reopen a letter of interpretation about the existence of wetlands on the site. “It is smack on top of wetlands,” he said, claiming that two separate surveys, in 1990 and 2011, indicated that this was the case. “This is illegal under state and federal laws and we will go to court on that.”

Christine Ferrara, senior public affairs officer at the IAS, said Mr. Afran misinterprets the agreement between the Institute and the Township. “Especially according to one member of the Planning Board, who was involved at the time of the settlement, his interpretation is incorrect,” she said. “Now, the colleagues on the Board have concurred. It is very clear-cut, in our view.”

Numerous residents of the neighborhood surrounding the IAS have spoken in favor of the plan in recent months, while Battlefield Society members have said it will desecrate the site of General George Washington’s counterattack and first victory against the British in the January 3, 1777 Battle of Princeton. The 15 faculty homes, eight of which are townhouses, will be located on seven acres, with an additional 10 acres adjacent to the Park to be preserved as public open space.

“Every vote in favor of the Institute’s plan is a vote against American history,” said William Tatum III, a scholar at the David Library of Washington Crossing, Pa. Battlefield Society member Brian Kovacs echoed Mr. Tatum’s views, calling approval of the proposal “misguided reasoning” and “an act against our heritage.”

Among those sympathetic to the proposal was Didier Fassin, the Institute’s James D. Wolfensohn Professor of Social Sciences. “This is an intellectual community, and to build an intellectual community one needs proximity,” he said, referring to the Institute’s preference that its scholars should be housed on site. Homes in the surrounding neighborhood have become too costly for faculty members, the Institute has said.

Mr. Afran’s claim about the existence of wetlands is based on a survey commissioned in 1990 by the IAS when it wanted to build housing on a different section of its property. That survey showed wetlands in the area where the housing approved last week is to be built, he said. The same person who did that survey was hired by the Battlefield Society last year. She found the same evidence of wetlands, he said.

“The Institute knew about these wetlands all along, but they concealed it,” Mr. Afran said. “The wetlands feed right into the Stony Brook and Lake Carnegie and our drinking water supply.”

The approved housing is to be built behind a buffer zone. According to the plan’s modifications, that buffer will be moved away from the edge of Battlefield Park and put directly behind the homes, shielding them from view and maintaining open space. The amendments also call for a path to be installed through the Institute property, with interpretive signage at the northern end about the Battle of Princeton; providing public access to the buffer zone; and reducing the size of one of the houses.

Before voting, members of the Planning Board expressed sympathy with both sides of the issue. But ultimately, the Institute plan won out.

“So many times, objectors who come before us have financial gain [as their purpose],” said Janet Stern. “Here, we have passion and zeal, and I’m wrestling with a lot of it …. Given that the Institute does own the land and that it does have the legal right to build …. I would support the application.”

Peter Madison said the application had to be viewed not just from an emotional point of view, but from a legal standpoint. The Battlefield Society would likely appeal a vote in favor of the proposal, he said. “But I believe if this application would go to court, I think the application has a much stronger case. So I will vote in favor.”

Mildred Trotman said, “As sympathetic as I am to supporters of the Battlefield, given all the information we have been given and the history of this project that goes back years and years, I feel confident supporting it.”

In a written statement, Institute Director Peter Goddard said the IAS was “immensely pleased” to have received approval. “This plan not only enables us to maintain the essential residential character of our community of scholars, but it will also enhance the Princeton Battlefield Park, which the Institute helped create and expand. We plan to work with others to promote the improvement of the interpretative materials in the park so that visitors might gain a greater understanding and appreciation of the Battle of Princeton. We look forward to partnering with local, state and regional bodies to that end.”

Mr. Afran said yesterday, “The hurdles against the Institute are immense at this point.”