Why can't the Pentagon budget be substantially cut?

I doubt that the committee charged to 'solve' our budget problems by November 23 will come to any meaningful conclusions. So, some cuts will automatically be made. Pentagon supporters are worried about this. However, both liberal and conservative think tanks have proposed plans that claim to support cuts from $800 billion to $1.2 trillion without damaging our military preparedness.

One argument the supporters make is that the 21st century wars have seen us wear out our equipment. It will cost a lot to replace and modernize equipment. However, from FY2001 to FY2010 the army spent $1 trillion to replace or upgrade its armored vehicles and the Air Force and navy met their modernization goals.

Lawrence Korb had a good summation of the situation in a recent NY Times letter:

Since we are unlikely to use nuclear weapons, our arsenal can be slashed from the current level of 5,000 to 311, as recommended by some Air Force strategists. Since we are withdrawing troops from the Middle East and are unlikely to need large armies there anytime soon, the size of our ground forces can be cut back by 100,000 to pre-9/11 levels. Since the cold war ended 20 years ago, the 80,000 troops still in Europe can be reduced to 20,000. Since the military increasingly relies on unmanned planes and precision guided munitions, the number of carriers and Air Force fighters can be reduced by 25 percent.

Finally, health care premiums for working-age military retirees can be doubled without breaking faith. In 1995, premiums were set at $460 a year for a family and never raised until a $60 increase this year.