National defense spending funds:
- The military (Army, Navy, Air Force, Marines, Space Force)
- Operations, training, and readiness
- Weapons systems and equipment
- Intelligence and national security support
It is one of the core and uniquely federal functions of government.
Scale
Current Spending: ~$917 billion (~13% of total federal spending; fourth largest category)
- Per person: ~$2,750
- Per household: ~$6,800
Recent / Proposed Levels: Recent budgets and proposals push defense spending toward or above ~$1 trillion annually, reflecting rising geopolitical tensions and modernization needs.
How It Works
Defense spending is part of the discretionary budget:
- Set annually by Congress and the President. .
- Can be increased or decreased through policy decisions.
This is different from programs like Social Security and Medicare, which run automatically.
Why It’s So Large
- The U.S. maintains a global military presence
- It plays a leading role in deterrence and security across allied nations
- Investments include: personnel, advanced technology and weapons systems, and global logistics and readiness
Many argue this is the one area where the federal government does something no other part of society can do, and there is no private-sector or state-level substitute for national defense.
Personnel & Force Size
The U.S. military is one of the largest organizations in the world.
Active-Duty Personnel (~1.3 million total):
- Army: ~450,000
- Navy: ~340,000
- Air Force: ~320,000
- Marine Corps: ~180,000
- Space Force: ~9,000
Reserve & National Guard:
- ~780,000 additional personnel
Civilian Workforce (Department of Defense):
- ~750,000 civilians
Total workforce tied to defense: ~2.8–3.0 million people
Personnel Costs:
- Roughly 20–25% of the defense budget (~$180B–$220B annually)
- Includes:
- Pay and housing allowances
- Healthcare (via TRICARE)
- Retirement pensions
Personnel is one of the largest single cost drivers—and one of the hardest to reduce quickly.
Where the Money Goes
Defense spending is divided into several major categories:
- Operations & Maintenance (O&M): ~40%
- Training, fuel, maintenance, logistics, base operations
- Military Personnel: ~20–25%
- Procurement: ~20–25%
- Ships, aircraft, vehicles, weapons systems
- Research & Development (RDT&E): ~10–15%
- Future technologies (AI, cyber, hypersonics, space)
- Military Construction & Family Housing: ~2–3%
The largest share is not weapons—it is keeping the force operating day to day.
Global Footprint
The U.S. maintains a worldwide network of installations.
Domestic Bases:
- Hundreds across the U.S. (major concentrations in Virginia, California, Texas, North Carolina, Florida)
Overseas Presence (~70–80 countries):
- Europe (Germany, UK, Italy, Spain)
- East Asia (Japan, South Korea, Guam)
- Middle East (Qatar, Bahrain, Kuwait)
Estimated Overseas Sites:
- ~750 total sites (large bases + smaller facilities)
This global footprint enables rapid response—but adds cost and complexity.
Fleet & Equipment Scale
Air Power
- ~13,000+ military aircraft total
- Largest air force in the world (U.S. Air Force)
- Second-largest air arm globally (U.S. Navy)
Key categories:
- Fighter jets (F-35, F-22, F/A-18)
- Bombers (B-52, B-2, B-21 in development)
- Transport and refueling aircraft
- Drones / unmanned systems
Naval Fleet
- ~290–300 deployable battle force ships
Major assets:
- 11 aircraft carriers
- ~90 destroyers and cruisers
- ~70 submarines (including nuclear-powered)
- Amphibious assault ships
Designed for global power projection, not just coastal defense.
Ground Forces
- ~4,500+ tanks (M1 Abrams and variants)
- Tens of thousands of armored vehicles
- Artillery, missile systems, air defense
Smaller than past eras, but more technologically advanced.
Cost of Major Systems
Modern systems are extremely expensive to develop and maintain:
- F-35 fighter jet: ~$80–100 million per aircraft (higher lifetime cost)
- Aircraft carrier: ~$13 billion to build (excluding aircraft)
- Virginia-class submarine: ~$3–4 billion each
- B-21 bomber (estimated): ~$700 million+ per aircraft
The trend is towards fewer systems, but far more capable—and far more expensive.
Long-Term Obligations Beyond the Core Budget
Defense-related costs extend beyond the annual defense budget.
Veterans Benefits:
- ~$300+ billion annually (Department of Veterans Affairs)
Military Retirement & Healthcare:
- Long-term pensions for career service members
- Healthcare for retirees and families
These costs are often tracked separately, but are part of the broader cost of defense.
Industrial Base & Supply Chain
Defense depends on a specialized industrial ecosystem:
- Major contractors (Lockheed Martin, RTX, Northrop Grumman)
- Thousands of smaller suppliers
- Shipyards, aerospace manufacturing, electronics
Key issue: Limited surge capacity (difficult to rapidly increase production of ships, munitions, and advanced systems). This has become a major constraint in recent conflicts and planning scenarios.
The Global Role (and Debate)
The United States is widely seen as the primary military backstop for much of the Western world and its allies.
- Provides deterrence against major conflicts.
- Supports alliance systems (e.g., NATO and others).
- Helps maintain global stability and trade security.
However, there is ongoing debate about:
- How large that role should be.
- Whether allies should take on more responsibility.
- The appropriate level of long-term spending.
Emerging Pressure Points
Recent events have highlighted constraints and rising competition:
- Limited capacity to replenish weapons and munitions quickly.
- Supply chain and industrial base challenges.
- Rising costs of modern warfare (technology, precision systems, etc.)
- Growing military investment by China, including rapid expansion of its defense budget, shipbuilding, missile forces, and broader military industrial base—paired with a long-term, state-driven planning horizon that contrasts with shorter U.S. budgeting and political cycles
This raises questions not just about spending levels, but readiness, capacity, and long-term competitiveness
What Makes Defense Different as a Budget Category
Defense is one of the few large areas of spending that is actively decided each year, not tied to automatic growth or demographics, and directly linked to strategic and geopolitical choices.
This makes it more flexible—but also more debated. Changes to defense spending involve:
- Security vs cost: Military strength and deterrence vs budget pressure.
- Global role: Leading role vs reduced international footprint.
- Near-term vs long-term: Immediate readiness vs modernization investments.
Defense budgeting is unusually difficult to evaluate from the outside. Much of the underlying strategic analysis, intelligence, threat assessment, and operational planning is not public, and many of the people making key decisions work with classified information that most citizens—and even many elected officials—never fully see.
In addition, military planning involves enormous uncertainty. Policymakers must make long-term decisions years or decades in advance about evolving technologies, future conflicts, industrial capacity, cyber threats, space capabilities, naval power, drones, missiles, artificial intelligence, nuclear deterrence, and the intentions of rival nations. It is often unclear which systems or strategies will prove most important in future conflicts.
This makes defense different from many domestic budget debates. While waste and inefficiency certainly exist and oversight matters, evaluating the “right” level and composition of defense spending is extraordinarily complex because success is often measured by deterrence and conflicts that never happen, rather than outcomes that are easy to observe directly.
The Bottom Line
National defense is a large, policy-driven part of the budget and one of the federal government’s most fundamental responsibilities. Its size reflects both America’s global role and strategic choices. Defense is a major expense, but it more pressure on long-term spending growth comes from the larger structural programs — healthcare, Social Security, and interest on the debt. While it is more flexible than other major spending categories, decisions about its level involve extremely complex and difficult tradeoffs among cost, security, and the role the U.S. chooses to play in the world.
Read next: Options for defense spending.