Campaigners hope to buy part of the site of one of the decisive battles of the Wars of the Roses to prevent it being built on in the future.
Two fields known as the Gastons – where the Battle of Tewkesbury was fought – have been put up for sale by Tewkesbury School's governors.
They are selling by informal tender, which means interested parties will not know what each other is bidding.
Members of Tewkesbury Battlefield Society want to put a bid in to try to prevent the land, part of the 1471 battleground, going to developers.
Although they suspect any bid to get planning permission for housing on the 10.5 acres of land would be rejected, they fear public access to it, such as for dog walking and wildlife watching, might be prevented.
The society has called a public meeting, at 7.30pm on Monday in Tewkesbury's Royal Hop Pole Hotel, to discuss what to do next.
Chairman Steve Goodchild said time was of the essence because bids had to be submitted by February 3.
He said: "The guide price for the land is between £120,000 and £150,000, far above the agricultural value of £70,000 to £80,000 – suggesting the estate agents think that developers might be interested."
With so little time to raise the money needed to put a bid in, he suspected a loan might have to be taken out.
He said: "We might have to get some kind of bridging loan."