The United States defence budget is the largest single element of the world’s military spending and one of the most consequential allocations of public money in the history of humanity. At approximately $886 billion for fiscal year 2025, it exceeds the combined defence spending of the next ten countries. Understanding where this money goes — the programmes, the contractors, the research priorities and the geopolitical logic that drives specific spending decisions — is essential for anyone seeking to understand American foreign policy, the defence industry and the global security environment.
The Structure of the US Defence Budget
The US defence budget is divided into several major categories. Operations and maintenance — keeping existing military forces trained, equipped and deployable — is the largest single line item, consuming approximately $300 billion annually. Personnel costs — salaries, benefits and healthcare for the 1.3 million active-duty service members and 800,000 civilians employed by the Department of Defence — account for approximately $180 billion. Procurement — the purchase of new weapons systems, aircraft, ships and vehicles — consumes approximately $170 billion. Research, development, test and evaluation — the investment in future military capabilities — receives approximately $140 billion. Military construction and family housing account for the remainder.
The Biggest Weapons Programmes
The F-35 Lightning II fighter jet, manufactured by Lockheed Martin, is the most expensive weapons programme in US history, with a lifetime cost estimated at over $1.7 trillion including procurement and operation across its planned service life. The programme involves purchases by the US Air Force, Navy and Marine Corps, as well as international partners including the UK, Australia, Japan, Israel and several NATO allies. Despite cost overruns and performance challenges, the F-35 remains the centrepiece of American tactical air power modernisation.
The Virginia-class nuclear attack submarine programme — built by General Dynamics and Huntington Ingalls Industries — represents one of America’s most important strategic investments in maintaining undersea dominance. At approximately $3.4 billion per vessel, the Virginia-class submarines are sophisticated enough to remain relevant into the 2060s. The AUKUS agreement — which commits the United States and United Kingdom to helping Australia acquire nuclear-powered submarines — will significantly expand submarine production requirements and spending.
Nuclear Weapons Modernisation: $50 Billion Annually
The modernisation of America’s nuclear arsenal — its land-based intercontinental ballistic missiles, submarine-launched ballistic missiles and air-dropped nuclear bombs — is one of the most significant and least publicly discussed elements of American defence spending. The Congressional Budget Office estimates that the United States will spend approximately $756 billion on nuclear forces over the decade from 2023-2032, an average of over $75 billion per year. The Sentinel programme, which will replace the aging Minuteman III ICBMs, has itself seen cost estimates balloon to over $140 billion — a significant overrun from initial projections.
Ukraine Aid: The Additional $100 Billion Commitment
Beyond the regular defence budget, the United States has committed approximately $175 billion in total assistance to Ukraine since Russia’s invasion, including approximately $75 billion in military assistance. This spending — authorised through supplemental appropriations rather than the regular defence budget — has provided Ukraine with artillery ammunition, anti-tank missiles, air defence systems, armoured vehicles and dozens of other capabilities essential to Ukraine’s continued ability to resist Russian aggression. Politically, the continuation of this support has been contested within the Republican Party, creating genuine uncertainty about the durability of American commitment that has been closely watched in Kyiv, Moscow and every European capital.
The Ripple Effect on the American Economy
Defence spending of this scale has significant macroeconomic and geographic consequences for the American economy. Defence contractors and their supply chains are heavily concentrated in specific states — Virginia (home to the Pentagon and large intelligence community), Connecticut (submarines), Texas (aviation and technology), California (aerospace and technology), Washington state (Boeing) and several others. The political economy of defence spending creates powerful incentives for members of Congress to protect contracts and bases in their districts, making rational programme cancellation — even for programmes that have failed to deliver — politically extremely difficult.
The defence industry is also one of America’s most important sources of advanced technology development. GPS, the internet, semiconductor miniaturisation and countless other technologies that underpin the modern economy originated in defence research funding. The question of whether the United States’ enormous defence spending represents good value for money — strategically, economically and technologically — is one of the most consequential public policy questions of our time.