Forty-six thousand British troops , one-third of the total strength of the British Army ( land forces ) , were active to assist with the invasion of Iraq and after that British armed forces were responsible for security in southern Iraq in the time before the Iraqi elections of January 2005 . Forty-six thousand British troops , one-third of the total strength of the British Army 's land forces , were deployed to assist with the invasion of Iraq and thereafter British armed forces were responsible for security in southern Iraq in the run-up to the Iraqi elections of January 2005 .