Tony Blair was warned there could be "long-term damage" to the armed forces unless Britain slashed its commitment to the Iraq War, a previously secret document revealed today
On the eve of the March 2003 invasion, foreign secretary Jack Straw and defence secretary Geoff Hoon told the then prime minister the UK had to cut its force levels by two-thirds by the autumn.
Mr Straw and Mr Hoon said keeping more troops in Iraq would be outside the Ministry of Defence's planning assumptions and would have an impact on other operations.
An extract from a previously classified letter from the Cabinet ministers to Mr Blair, dated March 19, 2003, was released today by the Iraq Inquiry.
Mr Straw and Mr Hoon wrote: "It will be necessary to draw down our current commitment to nearer a third by no later than autumn in order to avoid long-term damage to the armed forces.
"Keeping more forces in Iraq would be outside our current defence planning assumptions.
"If ministers wanted us to, we would need decisions now so that we would be able to recommend what would have to give elsewhere.
"Scaling down to nearer a third will limit our contribution thereafter to a maximum of around one brigade, a two-star headquarters and possible (sic) a contribution to higher level command and control, air and maritime components and support enablers.
"Our view is that we should probably agree now to tell the US, for planning purposes, that this is the upper limit of our contribution."
The UK's commitment to the Iraq campaign peaked at 46,000 troops in March and April 2003 and fell to around 18,000 by the end of May, according to MoD figures.
Tom McKane, the MoD's director general of resource and plans from 2002 to 2006, said Mr Straw and Mr Hoon's memo was sent amid concerns about the level and length of Britain's commitment to the conflict.
He told the inquiry: "It became apparent during that period that it was expected that there would be a substantial force retained in place after the fighting had been concluded, for a period of some six months or so, which would have obliged the UK to maintain something like a divisional strength force throughout that period, drawn down to a lower force level thereafter.
"That in itself would have constituted a breach in the planning assumptions."
Mr McKane said it was assumed at the time that the UK's military involvement in Iraq would last two to three years, with only an Army battle group-sized deployment - typically about 1,000 troops - by the end of that period.
Trevor Woolley, the MoD's financial director from 2003 to 2009, admitted that the armed forces were stretched by being involved in simultaneous major missions in Iraq and Afghanistan from 2006.
He said: "It was taking us quite considerably beyond the planning assumptions because the planning assumption was that one of the two medium-scale operations would not endure for more than six months.
"We had two that were enduring, and therefore that placed demands on the force structure that were over and above those that we had planned the force structure to be able to handle."
Nearly all British troops were withdrawn from Iraq by the middle of last year.
But Mr McKane said the military was still carrying out "recuperation", the process by which it returns itself to the state of readiness before a deployment.
Mr Woolley said no calculation had been made of the long-term cost to the UK of the large numbers of troops who suffered physical or mental injury as a result of their service in Iraq.
The inquiry was adjourned until Monday.Reuse content