In a new paper I’ve released for the Progressive Policy Institute, I advocate for a mid-range cut of $600-650 billion over ten years, or approximately ten percent of the Pentagon’s budget. So why is $600-650 billion the sweet spot?

First, let’s set the record straight: The Pentagon’s budget is not driving the deficit. Yes, military spending--particularly the $1.3 trillion bill for Iraq and Afghanistan--has unquestionably contributed to the debt, but that's a small percentage of the $14 trillion hole we’ve dug since 2001. Moreover, as deployments in Iraq and Afghanistan conclude in the coming years, the Pentagon’s share of the fiscal mess will decrease naturally.

Meanwhile, the debt’s real causes continue to surge. Entitlement spending is $1.6 trillion this year alone, and the Office of Management and Budget predicts it will increase to $2.2 trillion annually by 2016. Tax revenues continue to languish at historically pathetic levels, rising only 11 percent since 2001 despite a 47 percent increase in GDP over the same period.

Budget experts agree that the debt must be stabilized by saving $4 trillion over ten years, That's why the sequester is a double-whammy: If the supercommittee fails and the sequester is triggered, across-the-board automatic cuts in domestic and defense programs would only equal $2.5 trillion at most. In other words, if the supercommittee's members guard their ideological flanks, the sequester would eviscerate the Pentagon and the country would still be nearly $1.5 trillion shy of what it needs to save.

What's more, such a huge defense cut would have real implications for national strategy. Following World War II, America's political leaders made a crucial choice: The United States could draw on its unique combination of size, burgeoning economic might, and broad appeal of its democratic institutions to assume a role of global leadership.

Our nation has lead the way in anchoring regional balances of power, forging alliances with other democracies, and building international bodies charged with collective problem solving. While the military should not take credit for these accomplishments, it underpins and ultimately guarantees them.

If the Pentagon’s budget is cut by up to $1 trillion over ten years, DOD's baseline budget would fall to about 2.8 percent of GDP. While attempts to tie military spending to any specific level are somewhat arbitrary, a series of strategic reviews in the 1990s concluded that three percent of GDP was the minimum level of military spending required to continue to support this robustly internationalist vision of American foreign policy.

Despite recent calls, often justified on fiscal grounds, for more narrowly-defined national interests, there's scant evidence that the American people are clamoring for a retreat from the country's global leadership role.

Rather, the public seems more willing to support President Obama's call for shared sacrifice to control national spending. In a summer Washington Post-ABC poll, a majority of Americans said they supported increases to taxes on the wealthy. Although Medicare remains a touchy subject especially for Democrats, a June CBS poll found half of respondents would entertain changes to the program. Indeed, everything—entitlements, taxes, and domestic spending (including defense)--must be on the table.

That's exactly where a $450 billion cut falls short: the Pentagon can achieve it by slowing the rate of its budget's growth, rather than making absolute reductions to its bottomline. Without a real net reduction that forces harder choices than Secretary Panetta alluded to, the Pentagon wouldn't be a full partner in solving a sweeping national problem.

A reduction of just over $600-$650 billion strikes the right balance. It would be large enough to make a real contribution to deficit reduction in the spirit of shared sacrifice while small enough to avoid big strategic changes in the nation's foreign policy.

Jim Arkedis directs the National Security Project at the Progressive Policy Institute.