The site of a decisive battle in the Wars of the Roses in Northampton, earmarked for sports pitches, is to be examined for historical remains.
The Battlefields Trust has campaigned for a survey of the 85-acre Delapre Park for many years.
Artillery was used for the first time in warfare during the battle between the Houses of York and Lancaster in 1460.
Bodies of soldiers are buried there and the position of a rare battlefield fortification needs to be discovered.
The site has never been fully explored and is now under threat from development.
Northampton Borough Council, which owns the site, has agreed a survey will take place before any development begins.
The Battlefields Trust believes any decision on laying pitches and building facilities should be made after a survey and an evaluation of the site's historical significance.
Northampton Saints rugby and the town's football club are keen to use the land at Eagle Drive.
A trust also wants to create a memorial pitch there in honour of Northampton-born footballer Richard Butcher who died of a rare heart condition aged 29.
The borough council has agreed in principle to its development as a community amenity but has attracted criticism from English Heritage and local businesses.
The Battlefields Trust believes valuable artefacts such as early cannon balls and weapons in the top soil could be lost forever during excavations and landscaping.
Mike Ingram, from the trust, said the battle fought there was decisive in English history changing the line of kings from Lancastrian to Yorkist.
The future Edward IV, leading a Yorkist army, routed the Lancastrians in the battle, captured King Henry VI and seized the throne.
Mr Ingram said: "It's a unique site because of the use of artillery and a fortified camp set up by the Lancastrians which the Yorkists successfully captured.
"No work has been done to set out accurately the battlefield area or explore its unique features.
"There are bodies buried there and evidence of the battle, such as lead balls from the artillery, in the top soil.
"Building sports pitches, changing rooms, parking areas and roads could destroy this buried evidence."
A spokesman for Northampton Borough Council said: "If the plan to develop the sports pitches goes ahead, we have said that we will undertake a large piece of work to understand exactly where the battlefield was and find out more about it.
"We would also prepare a thorough conservation management plan to protect and conserve the battlefield site, in conjunction with English Heritage and other parties such as the Battlefields Trust.
"We have always stressed the site is extremely important to us and a key part of the Northampton Alive regeneration programme."
Plans for the site are tied up with developments at Northampton Saints Franklin's Gardens stadium where a new North Stand is planned to expand seating.
This is to be paid for by an extension to the superstore at the stadium.
To allow the expansion, the Saints want to move two community pitches to Eagle Drive.
One local business could also be seriously affected by the development.
Jane Allwork, whose family have run a riding school and stables business on the Eagle Drive land for 25 years, is worried about the plans.
The business has grazing rights for its 30 horses and ponies on Delapre Park land that was managed as a farm by Mrs Allwork's father and grandfather.
"We are the last riding school and livery business left in Northampton," Mrs Allwork said.
She runs the business with her daughter Lucy Clifton and said the borough council had talked about moving them to land close to a nearby hotel.
"The drainage there is poor and it would be cut up in no time. It is also too near the dual carriageway and that would threaten the security of the horses," she said.