Post-9/11 wars cost US about $8 trillion: Is Trump ready to spend more for 'peace'?

As the world continues to struggle with one conflict after another, a report by Brown University’s Watson School of International Public Affairs elucidated the cost of war incurred by one of the most powerful countries in the world, the United States of America. The report specifically focused on the US involvement in conflicts that took place after the devastating 9/11 terror attack.

An analysis of the impact of global wars on the US becomes important to assess since it is coming at a time when the US has interfered in several conflict hotspots around the world, especially under US President Donald Trump. Most recently, the US toppled the draconian regime of Venezuelan President Nicolas Maduro by outright capturing the president from the Latin American nation’s capital.

Since then, he has been issuing threats to Iran, Colombia and especially Greenland, which belongs to Denmark, America’s long-term ally. All this is happening against the backdrop of a turbulent world. While the Russia-Ukraine war is still raging on, despite continuous efforts of peace talks, the war in Gaza has de-escalated only to a certain extent.

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This made many wonder if the US is back to the “Bush-era” where it is getting into the battles that were not there in the first place. This also begs the question of how much of a cost the involvement in these conflicts is incurring to the US. As America continues to increase its defence spending to record numbers, it also becomes important to assess how much these conflicts are costing the average American citizen. Here’s a look at the analysis.

Post 9/11 cost of war

While Trump is getting the US intervene in several conflicts around the world, the Brown University assessment only dealt with the post 9/11 wars and comprises data obtained in 2021 when former US President Joe Biden was in power. As per the report, the cost of the post-9/11 wars in Iraq, Afghanistan, Pakistan, Syria, and elsewhere totals about $8 trillion.

This included the estimated direct and indirect costs of spending in the United States post-9/11 war zones, homeland security efforts for counterterrorism, and interest payments on war borrowing. Costs for medical care and disability payments for veterans are the largest long-term expense of the post-9/11 wars.

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However, the estimate does not include spending by the dozens of United States allies, including Australia, Britain, Canada, Denmark, Italy, the Netherlands, Romania, Germany and France. If the U.S. had not had the support of those allies, it would likely have spent more on those wars (and arguably taken more casualties).4 This estimate also does not include spending by state and local governments within the US for counterterrorism or services for post-9/11 war veterans. This report also does not factor in future interest costs on borrowing for the wars.

Breakdown of spending

When it comes to pre-Trump era post 9/11 war spending, the breakdown would be as follows:

1) Direct war appropriations

According to the report, the US Department of Defence, including Overseas Contingency Operations (OCO, has incurred $2.1 trillion in these wars. Meanwhile, the US State Department had spent - $189 billion in war-related aid. Most of these amounts have been spent in Afghanistan, Pakistan, Iraq, Syria, Somalia and other African nations.

2) Domestic counterterrorism efforts

Following 9/11, the Department of Homeland Security & Domestic Counterterrorism has spent $1.1 trillion. This included the creation of the Department of Homeland Security, expanded surveillance, and domestic counterterror programs.

3) Budget increases of the Pentagon 

There has been $884 billion in permanent increases tied to war requirements. War funding blurred into “enduring requirements,” raising baseline military spending even after troops withdrew from a particular base.

4) Veterans’ Care

It is important to note that $465 billion was spent through FY2022 on medical and disability care. The Brown University study projected a future obligation of a whopping $2.2–2.5 trillion through 2050. Apart from this, disability claims are at historically high rates, with many veterans requiring lifelong support.

5) Interest on Borrowing

$1.087 trillion already paid in interest through FY2022. Because wars were financed without war taxes or bonds, debt servicing will continue to add hundreds of billions more in the future.

Impact on American taxpayers

Just like other countries around the world, the US also get the money to deal with these wars through American taxpayers. In March of 2021, the Department of Defence concluded in its most recent public estimate that emergency/overseas contingency operations (OCO) spending for the wars in Iraq, Syria, and Afghanistan cost a total of $1.596 Trillion, or $8,094 per taxpayer through FY 2020. However, as the DOD notes, “these amounts exclude non-Department of Defence classified programs.”

It becomes important to highlight these costs because they significantly affect:

- Opportunity costs: Every household’s share could have funded healthcare, education, or infrastructure instead.

- Debt burden: Because wars were financed by borrowing, much of this cost is paid in interest, not direct services.

- Veterans’ care: These obligations will continue for decades, meaning future taxpayers will still be paying long after the wars themselves ended.

Let’s look at it from a wider perspective; the United States spends - $800 billion annually on defence, so the wars added a massive extra layer. In comparison to this, the entire federal education budget is about $80 billion per year, meaning war costs equal 100 years of education spending.

The US’s inclination towards Israel

Boston University’s report also pointed out how, after October 7, 2023, the US has spent $21.7 billion in military aid to Israel. Apart from this, $9.65–12.07 billion has been spent on operations in Yemen and the wider region.

When it comes to economic tradeoffs, military spending creates ~5 jobs per $1 million, compared to 13 in education, 9 in healthcare, and 7–8 in infrastructure/clean energy. While Trump has brokered a ceasefire deal between Israel and Hamas, tensions have been ripe between Israel and other West Asian nations, especially Iran. Hence, this cost is expected to rise this financial year as well.

Implications

These wars and conflicts have the following implications, some of which hit close to the United States as well:

- Humanitarian crisis: Millions killed, injured, or displaced. The conflicts have a greater humanitarian impact and often lead to a breach of international laws. The US intervention in other conflicts would also put American troops’ lives at risk.
- Economic burden: The US has spent trillions on war in other nations instead of domestic priorities. As mentioned before, this money could have helped provide a much-needed boost to the American education and other infrastructure sectors.
- Veteran care: Long‑term costs and mental health challenges remain unresolved. The cost of this is expected to increase in the future.
- Environmental damage: Military operations contribute heavily to global emissions.
- Democratic erosion: Civil liberties weakened undera prolonged war footing.

With Trump pushing for ceasefire deals in a bid to bag a Nobel Peace Prize, it’ll be interesting to see if he will spend more on “peace” or not.