Much of the US Military increase has to do with "Quality of Life" issues for enlisted personell and their dependents, also spares and maintenance have been neglected for years to fund lots of deployments. (Haiti, Kosovo, Bosnia, etc.).
Also don't think the US is blindly spending to make Republicans who are connected to Military contractors happy, in truth Secretary of Defense Rumsfeld has done an outstanding job focusing on Re-structuring and streamling the Department of Defense and the various branches.
One such case is the Crusader, a highly sophisticated self propelled artillery piece the US Army wanted. Many high ranking Republicans who's districts would get work from the Crusader project pressed hard. Even the Secretary of the Army stepped on alot of Administrations toes when he went over Secretary Rumsfields head straight to Congress to lobby for the Crusader, the Bush administration and Rumsfeld in particualr are strongly against the because of it's costs.
Secretary of Defense Rumsfeld is focusing more on technology and quality of life improvements (better pay, housing, health care etc) for enlisted personell, while cutting such popular projects such as the Crusader.
Also the V-22 Opsrey program which the Marines, Army and the Air Force said they wish they had for the recent Afghanistan campaign was originally cancelled by Cheney when he was Secretary of Defense under President George HW. Bush. The Congress later restored funding.
Congress tried desperatley (both Democrats and Republicans) to restore the Crusaders funding, but the Administration blocked their efforts.
Also it' Rumsfield who has been trying to retire about half of the B-1 Bomber fleet which has the Air Force and the National Guard units which operate them upset. Rumsfield actually was a big part in Developing the B-1 under President Gerald Ford, and he actually piloted a few on test flights.
So to say the administration is just spending to spend is totally inaccurate, on the contrary many (inlcuding myself) feel they are cutting too much. However I also believe the investements they are making long term will pay off big time.
The Administration and Secretary Rumsfield in particular are doing an excellent job of restructing the Forces to be lighter and more mobile while at the same time making tremedous investments in technology research and Development.
For more about the Crusader check out this site http://www.teamcrusader.com/