The Government has confirmed that Custume Barracks in Athlone is to lose its brigade headquarter status.
The decision comes after the coalition decided to cut the number of brigades to just two, which are to be headquartered in Cork and Dublin.
However the Government has insisted that 1,000 soldiers will be kept at the midlands facility.
Junior defence minister Paul Kehoe made the announcement in the Dáil this afternoon.
"I can confirm here today that the brigade headquarters for the two new brigades will be located in Cork and Dublin," he said.
"I can also confirm that within an overall strength of 9,500, the numbers serving in Custume Barracks will be in the order of 1,000 personnel.
"The new arrangements with regard to the brigades will have no dramatic impact on the numbers in Custume Barracks."
Fianna Fáil's defence spokesman Dara Calleary however said the decision to axe the Western Brigade of the Defence Forces is a devastating blow for Co Westmeath and will have implications right across the west of Ireland.
"Given the lack of consultation around this announcement, one wonders what further plans the Government has for the organisation of the army," Deputy Calleary said.
“This is essentially a downgrading of the Defence Forces in the west," he added.
"There are currently 1,400 personnel attached to Custume Barracks and the Government will now only give a commitment to retaining 1,000 of them.
“I am disgusted that the wonderful tradition of service from the West has been undermined in this way.”