Five infantry battalions are expected to be axed and other units merged or turned into reservists in the biggest overhaul of the Army in more than a century, under plans to be announced on Thursday.
Defence Secretary Philip Hammond will set out how the regular Army will be cut from 102,000 troops to 82,000 by the end of the decade - its lowest level since the Napoleonic Wars.
The plan - known as Army 2020 - is expected to see it split into two, with a reaction force, ready to respond to emergencies around the globe, and an adaptable force capable of carrying out a range of tasks and commitments.
Mr Hammond has said the changes - drawn up by Lieutenant General Nick Carter - will provide the basis of a smaller, more flexible and agile Army into the future.
But the prospect of losing historic units has been the cause of intense anguish within the service.
The Daily Telegraph disclosed this week that one officer, Brigadier David Paterson of the Royal Regiment of Fusiliers, had written to the head of the Army expressing his bitter disappointment at plans to axe one of its two battalions.
In his letter to General Sir Peter Wall, Chief of the General Staff, Brig Paterson said the proposal "cannot be presented as the best or most sensible military option".
Other units under threat are reported to include the Yorkshire Regiment, the Royal Regiment of Scotland, the Royal Welsh and the Mercian Regiment.
Mr Hammond, who will set out details of the proposals in a statement to the House of Commons, has acknowledged that they have involved some "difficult" decisions.
But he said that cuts could not be avoided, with the demands for strict financial discipline under the Government's 2010 Strategic Defence and Security Review.
Under the plans, reductions in regular Army strength would be offset by increases in part-time reservists, with the Territorial Army doubling in numbers from 15,000 to 30,000.
As well as providing specialist capabilities - such as medics and intelligence - reservists would be used to reinforce infantry battalions on deployment.
The Army would also be required to make greater use of civilian contractors in areas such as logistics support in order to concentrate military capability on the frontline.