Standard inflation isn't a relevant measure in the defence sector as the increasingly technological nature of military equipment means that defence inflation runs well above RPI. This means that defence spending has been cut in real terms every year of this government. It has also fallen as a % of total spending as the following chart shows.
It's worth noting that we've had a couple of wars on the go recently as well. Going to war is far more expensive than not going to war and this massive increase in expenditure has not been matched by an increase in funding.
Brown says that he gave the defence chiefs everything that they asked for, they say he didn't. I know who I believe.