Concerns were raised about the number of helicopters available to British forces even before the UK expanded its mission in Afghanistan, the Iraq Inquiry heard today.
Des Browne, who was defence secretary from May 2006 to October 2008, said being able to move troops by air became ever more important as the nature of the threat changed "dramatically".
But he said he did not "necessarily" accept that the shortage of helicopters led to greater use of lightly-armoured Snatch Land Rovers.
Mr Browne also admitted that he found it difficult to come to terms with the deaths of British troops in Iraq.
He told the inquiry he had only been in the job for 24 hours when a Lynx helicopter was shot down over the southern city of Basra, killing five UK personnel.
He said: "I hadn't the benefit of military experience, which helps people to cope.
"I think at the strategic level I found it difficult personally to deal with the losses of our people in the operational theatre.
"I became focused, I think rightly, on our people and their families and on our support for them during the time that I had this awesome responsibility."
Inquiry panel member Professor Sir Lawrence Freedman asked him: "Would you accept that even before the commitments to Afghanistan, there was concern already being expressed that we simply didn't have enough helicopters to perform the military tasks that we had set for ourselves."
Mr Browne replied: "Yes, there was concern being expressed."
He went on: "I recognised the importance and the increasing importance of helicopters from the point of view of secure transport.
"The more the nature of the risk adapted and changed - and it changed quite dramatically in the time that I was secretary of state for defence - the more important it became for us to be able to move in the air as opposed to on the ground."