On Monday afternoon, President Obama 
will nominate
 former Nebraska senator Chuck Hagel (R) as secretary of defense. The 
confirmation hearings are likely to focus on Hagel’s views on Israel and
 Iran. Yet the biggest headache likely to face the next defense 
secretary will almost certainly be the U.S. military budget.

Former senator Chuck Hagel. We’ll make thiiiiiis much in cuts. (Lauren Victoria Burke/Associated Press)
 
The United States spends far more than any other country on defense 
and security. Since 2001, the base defense budget has soared from $287 
billion to $530 billion — and that’s before accounting for the primary 
costs of the Iraq and Afghanistan wars. But now that those wars are 
ending and austerity is back in vogue, the Pentagon will have to start 
tightening its belt in 2013 and beyond. If Hagel gets confirmed as 
secretary of defense, he’ll have to figure out how best to do that.
Below, we’ve provided an overview of the U.S. defense budget — to get
 a better sense for what we spend on, and where Hagel might have to cut:
1) The United States spent 20 percent of the federal budget on defense in 2011. 

All told, the U.S. government 
spent about $718 billion
 on defense and international security assistance in 2011 — more than it
 spent on Medicare. That includes all of the Pentagon’s underlying costs
 as well as the price tag for the wars in Iraq and Afghanistan, which 
came to $159 billion in 2011. It also includes arms transfers to foreign
 governments.
(Note that this figure does not, however, include benefits for 
veterans, which came to $127 billion in 2011, or about 3.5 percent of 
the federal budget. If you count those benefits as “defense spending,” 
then the number goes up significantly.)
U.S. defense spending 
is expected
 to have risen in 2012, to about $729 billion, and then is set to fall 
in 2013 to $716 billion, as spending caps start kicking in.
2) Defense spending has risen dramatically since 9/11.

Here’s 
a historical chart
 of U.S. defense spending since World War II in inflation-adjusted 
dollars. There’s a big spike for the Korean and Vietnam wars. There’s 
another big ramp-up during the 1980s under President Reagan. Then 
defense spending got cut significantly during the Clinton years until 
soaring to historically unprecedented levels after 9/11.
U.S. defense spending is set to fall again in 2013, though it will 
still be as high in real terms as it was at the height of the Reagan 
build-up for the foreseeable future.
3) The Pentagon’s budget mostly consists of personnel pay, weapons procurement, and operations.

Source: Office of Management and Budget, Graph: Dylan Matthews
 
In 2011, the Pentagon 
spent
 about $161 billion on personnel pay and housing, $128 billion on 
weapons procurement, and $291 billion on operations and maintenance— the
 last largely in Iraq and Afghanistan. Those three items made up the 
bulk of the budget. Smaller amounts also were spent on R&D (about 
$74 billion) and nuclear programs ($20 billion), as well as 
construction, family housing and other programs ($22 billion).
My colleague Dylan Matthews created the graph above to show how these
 portions have changed over time. Personnel spending has stayed constant
 over the years, even as the number of soldiers in the U.S. military has
 shrunk (pay and benefits have increased). Weapons procurement can vary 
wildly. And operations spending has soared during the wars in Iraq and 
Afghanistan.
4) The United States spent more on its military than the next 13 nations combined in 2011.

Needless to say, the United States remains the world’s dominant military power. The graph above 
comes from the Pete G. Peterson Foundation, which compiled data from the Stockholm International Peace Research Institute.
5) The U.S. defense budget is poised to shrink in 2013 and 
beyond, although this won’t be the biggest downsizing it has ever faced.

Two big things are about to happen to military spending. The wars in 
Iraq and Afghanistan are winding down. And, thanks to the 2011 Budget 
Control Act, the Pentagon is facing both hard budget caps and a looming 
sequester that would cut defense spending by about $1 trillion over the 
next decade (compared to what was expected).
That’s a serious cut. Although, as the graph above from the 
Center for Strategic and International Studies shows,
 even if the sequester is fully implemented, which no one expects, the 
drawdowns after Korea, Vietnam and the Cold War were far more drastic in
 inflation-adjusted dollars.
6) Sequester or no sequester, the 2011 Budget Control Act is 
expected to rein in the Pentagon’s base budget over the next decade:

The chart above 
comes from
 the Congressional Budget Office,* which points out that the spending 
caps in the Budget Control Act of 2011 are likely to force the 
Pentagon’s “base” budget to stay virtually flat in the next decade, 
adjusting for inflation (that’s the light-blue dashed line). If Congress
 fails to avert the sequester, then funding levels will drop to an even 
lower level (that’s the light-blue solid line).
These numbers don’t include any additional war funding that Congress 
might approve over the next decade. Still, sequester or no sequester, 
the Pentagon’s base budget will be well below the dark blue solid line, 
which is the CBO’s projection of what the Department of Defense’s budget
 would look like if costs remained “consistent with DoD’s recent 
experience.”
7) The Pentagon and Congress are already rejiggering the military budget in response to austerity.

Photo: Raytheon
 
Back in January, the Department of Defense unveiled its proposed 
budget for fiscal year 2013 — a look at how it would deal with new 
budget constraints. As Wired’s Spencer Ackerman 
reported,
 the Pentagon wanted to downsize about 100,000 human soldiers and ramp 
up advanced weapons programs, including drones, bombers and missiles.
Of course, the Pentagon doesn’t have the final say. Congress eventually passed its own 
$631 billion defense appropriations bill
 in December that made some changes to the Pentagon’s vision. Many of 
the weapons systems that the Obama administration wanted to retire — 
such as three Navy cruisers — were kept in. The final did, however, make
 plans to reduce civilian and contractor personnel by 5 percent over the
 next five years.
8) The next secretary of defense will have to make further tough choices about the Pentagon’s budget.

The chart above comes from 
a recent report
 from the Center for Strategic and Budgetary Assessments, which asked 
seven teams of experts to come up with ways to meet the Pentagon’s new 
spending constraints in the coming decades. It shows what areas 
different teams would cut — some experts advised heavily slashing the 
civilian workforce, others advocated cutting aircraft inventory. (There 
were some areas of consensus, though: surface ships were generally cut 
more than submarines, for instance.)
The cuts weren’t always painless. For instance: “Five of seven teams 
agreed that they could not fully resource their strategies under the 
assumed fiscal guidance unless they accepted near-term risk by reducing 
current readiness programs.” These are trade-offs Hagel will have to 
navigate.
9) Ordinary Americans want to cut defense spending far more than is already on the table,

Back in May, the Stimson Center 
unveiled the results
 of a new survey asking U.S. voters about their views on defense 
spending. As it turns out, Democratic, Republican and independent voters
 all want to cut military spending far more severely than the sequester 
would and far, 
far more severely than either party has 
proposed. Congress isn’t likely to pay much attention here, but it’s a 
reminder that defense cuts tend to be extremely popular.
* 
Correction: I replaced the original graph
 in #6 with a better chart from the Congressional Budget Office, which 
shows military spending shrinking over the next decade under the 2011 
Budget Control Act (after adjusting for inflation), not growing as 
originally stated. Apologies for the error.