When Mr. Rumsfeld took over at the Pentagon in 2001 he had a mandate from President Bush to begin to transform the military from the Cold War force it had remained even as it had shrunk by about half during the 1990's. Officials in the Obama administration have tried to characterize the recent plans for massive budget cuts to military spending as somehow a continuation of the Bush/Rumsfeld transformation. However, this clearly wrong since one of the first things Mr. Rumsfeld did was request a sizable increase in funding. In the spring and summer of 2001 most congressmen were not eager to act on this, but of course that changed after 9/11.
Significant increases were approved by congress; there was enough money to fight in Afghanistan and Iraq and offer assistance in the Philippines and the Horn of Africa, but there was no big defense buildup as was seen under President Reagan in the 1980s. Equipment and personnel were replaced but there was not significant beefing up of forces. For example, Rumsfeld's successor Secretary Gates cut back production on the F-22 and Secretary Panetta has recently slowed production of the the F-35. Everyone complained about not having enough troops to fight the GWOT, but the Bush administration never made a big push to increase the ranks and the Obama administration wants to actually reduce the Army and Marine Corps.
The Obama policy might be cynically summarized as an attempt to weaken the military to the point that it is no longer a question of should we engage an enemy like Iran?, but can we? A smaller military with aging equipment will be seen as less and less capable of mounting effective offensive operations. The administration insists the force will not be hollowed out but what will we have in five or ten years when we have not begun to make serious spending commitments for new weapons like next generation tanks, attack helicopters and long range bombers? What about a replacement for the M4/M16 that offers more firepower? Is all of this going to be left in limbo until drones are deployed to replace most of the manned systems? Rumsfeld's Pentagon unveiled an ambitious program of next generation upgrades and weapons procurements, but these were mostly canceled by the Obama administration. The legacy of Defense Secretary Panetta remains to be seen but it does but it does not appear to be one of a resurgent and reinvigorated military, it feels like it will be more like the apathy of the 1970s.