Thirty two UK troops died as a result of the war
As Britain's most senior military officer warns that the UK's armed forces could not easily go to war for 18 months, BBC News Online looks at the problems facing the armed forces in the wake of the Iraq conflict.
In the days of the British Empire, Britain's armed forces were spread across six continents and were often involved in several conflicts simultaneously.
Now, in the wake of the Iraq conflict, the chief of the defence staff says they would be unable to fight a major conflict for 18 months.
UK forces abroad
Armed forces total: 206,930
Northern Ireland: 13,500
Bosnia and Croatia: 1,249
Macedonia and Kosovo: 789
Other UN missions: 442
War is far more complicated and technologically advanced now than in the 19th century.
After the Boer War the British Army's main concern was the need to replenish its stock of horses, hundreds of which had died on the South African veld.
But buying up and training horses is a relatively quick and simple job compared with replacing a £5.6m Challenger 2 tank.
The war in Iraq came at a bad time for the British Army, which was already stretched with covering for the fire dispute and had been heavily involved in last year's campaign against al-Qaeda and the Taleban in Afghanistan.
Large amounts of leave was cancelled because of the fire strike and more was lost as a result of the Iraq campaign.
Now many soldiers, marines and airmen will be due leave with their families back home.
A quarter of the British Army - 26,000 troops - were committed to Operation Telic, as the Iraq campaign was officially known.
The real problem, as we are seeing now in Iraq, is that there continues to be a task which requires military personnel in large numbers
But another 19,000 servicemen and women from the Royal Navy, Royal Marines and Royal Air Force were involved in the conflict in some part.
Although the war only lasted a month many British service personnel remain in Iraq where they are keeping the peace, maintaining law and order and helping with humanitarian work.
At some point many of the men who fought in the war will be relieved by fresh regiments brought in from Britain, Germany or Northern Ireland.
British soldiers remember their dead in Iraq
Former Assistant Chief of Defence Staff, Air Marshal Sir Timothy Garden, told the BBC the armed forces was already stretched before the conflict began, partly because of a problem with retention of personnel.
He said: "The real problem, as we are seeing now in Iraq, is that there continues to be a task which requires military personnel in large numbers if you are to re-form the rule of law, put in troops to mend the infrastructure and allow a democracy to occur.
"We failed to do it in Afghanistan properly; we did it quite well in the Balkans.
"But these are tasks that need people, so the army does still need more people plus equipment that is delivered on time and is affordable."
Sir Timothy said: "Most of these are wars of choice but our government seems to choose to go an do them. If it wants the military to be available it's going to have to pay the bill."