From D-Day to Desert Storm: The Most Expensive Wars in U.S. History

Under the terms of the United States Constitution, the power to declare war rests solely with Congress, the same branch of government that also controls federal spending. While these two powers are separate and distinct, an exercise of the former has always had a direct impact on the latter. Indeed, the United States has spent trillions of taxpayer dollars on warfare over the course of its 250-year history, 

Even during peacetime, the United States invests more in its military than any other country on Earth. According to the Stockholm International Peace Research Institute, total U.S. defense spending topped $997 billion in 2024 alone, more than triple the defense budget of the world’s second highest-spending military power, China. As of 2023, the latest year of available data from the World Bank, U.S. military spending was equivalent to roughly 3.4% of gross domestic product, a full percentage point above the 2.4% global average. 

For any country, government budgets are often a reflection of national priorities — and in the United States, heavy investment in the military serves multiple purposes. By maintaining its ability to project power across the globe, American defense spending better positions the U.S. to succeed should war break out. Perhaps even more importantly, the billions of dollars the Pentagon spends each year on weapons development and procurement also act as a deterrent to adversarial nations and may ultimately reduce the likelihood of war.

Military spending necessitated by war goes well beyond what is typically included in a peacetime defense budget. From troop mobilization and deployment to equipment repair and munitions procurement, waging a war is always a strain on the nation’s financial resources. Among the major conflicts the United States has engaged in, estimated inflation-adjusted costs have ranged from about $1.7 billion to more than $6 trillion.

Using data from the Naval History and Heritage Command and the U.S. Department of Defense, 24/7 Wall St. identified the most expensive wars in U.S. history. We ranked 12 major wars involving the United States on their reported financial cost, adjusted for inflation. For the American Civil War, the Union and Confederate militaries each have their own cost estimates. All inflation adjustments reflect estimated costs in current 2025 dollars. Supplemental data on U.S. troop commitments and casualties, when available, are from the U.S. Department of Veterans Affairs and the DOD. Due to differences in accounting methodology and inflation rate revisions, the estimates in this story may vary from those reported in other sources. 

The most expensive conflicts on this list took place primarily in the 20th century, largely due to the rapid development of military technology during that period. Up until the mid-1800s, the weapons of war — including swords, muzzle-loading firearms, and artillery — had remained largely unchanged for hundreds of years. By the late 19th century, repeating firearms that used self-contained cartridges had been widely adopted, and during the First and Second World Wars, military powers were deploying tanks, aircraft, and submarines into battle. So far in the 21st century, the weapons of war — which now include unmanned drones and space-based satellites — have continued to evolve, and their costs have continued to grow.

The wars in Iraq, Afghanistan, and Vietnam are three of the highest-ranking conflicts on this list. Each spanned multiple decades, and their costs are attributable in no small part to their length. Notably, none of these wars involved a formal declaration of war by Congress; instead, Congress passed Authorizations for Use of Military Force for Iraq and Afghanistan. The Vietnam War was conducted under the Gulf of Tonkin Resolution. 

The last time Congress officially declared war was at the outset of U.S. involvement in World War II — which, to this day, stands as the most expensive war in American history. World War II was a multi-theater conflict that saw over 16 million American troops deployed across the globe. The Allied effort was also supported on the home front by the full weight of American industry.

These are the most expensive wars in U.S. history. 

Why It Matters

The loss of human life is the most tragic and costly dimension of any armed conflict. From the American Revolution to the War in Afghanistan, hundreds of thousands of American troops have been killed in battle. While secondary to the human toll, war is also an economic strain. According to estimates based on Defense Department reports, the U.S. has spent trillions of inflation-adjusted dollars on waging war—and a handful of conflicts in American history account for the bulk of that expense.

13. War of 1812 (1812-1815)

• Approx. cost to the U.S. in 2025 dollars: $1.7 billion
• Approx. cost to the U.S. during conflict: $90.0 million
• Peak year of war spending during conflict: 1813 (2.2% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 286,730 troops
• Total battle deaths of U.S. service members: 2,260 fatalities
• Other deaths of U.S. service members associated with conflict: N/A
• American troops who suffered non-fatal wounds: 4,505 wounded

12. Mexican War (1846-1849)

• Approx. cost to the U.S. in 2025 dollars: $2.7 billion
• Approx. cost to the U.S. during conflict: $71.0 million
• Peak year of war spending during conflict: 1847 (1.4% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 78,718 troops
• Total battle deaths of U.S. service members: 1,733 fatalities
• Other deaths of U.S. service members associated with conflict: 11,550 fatalities
• American troops who suffered non-fatal wounds: 4,152 wounded

11. American Revolution (1775-1783)

• Approx. cost to the U.S. in 2025 dollars: $2.7 billion
• Approx. cost to the U.S. during conflict: $101.0 million
• Peak year of war spending during conflict: N/A
• Total U.S. service men and women deployed in conflict: 217,000 troops
• Total battle deaths of U.S. service members: 4,435 fatalities
• Other deaths of U.S. service members associated with conflict: N/A
• American troops who suffered non-fatal wounds: 6,188 wounded

10. Spanish American War (1898-1899)

• Approx. cost to the U.S. in 2025 dollars: $10.1 billion
• Approx. cost to the U.S. during conflict: $283.0 million
• Peak year of war spending during conflict: 1899 (1.1% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 306,760 troops
• Total battle deaths of U.S. service members: 385 fatalities
• Other deaths of U.S. service members associated with conflict: 2,061 fatalities
• American troops who suffered non-fatal wounds: 1,662 wounded

9. Civil War: Confederacy (1861-1865)

• Approx. cost to the U.S. in 2025 dollars: $22.5 billion
• Approx. cost to the U.S. during conflict: $1.0 billion
• Peak year of war spending during conflict: N/A
• Total U.S. service men and women deployed in conflict: 1,050,000 troops
• Total battle deaths of U.S. service members: 74,524 fatalities
• Other deaths of U.S. service members associated with conflict: 59,297 fatalities
• American troops who suffered non-fatal wounds: Unknown

8. Civil War: Union (1861-1865)

• Approx. cost to the U.S. in 2025 dollars: $66.7 billion
• Approx. cost to the U.S. during conflict: $3.2 billion
• Peak year of war spending during conflict: 1865 (11.3% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 2,213,363 troops
• Total battle deaths of U.S. service members: 140,414 fatalities
• Other deaths of U.S. service members associated with conflict: 244,097 fatalities
• American troops who suffered non-fatal wounds: 281,881 wounded

7. Desert Storm (1990-1991)

• Approx. cost to the U.S. in 2025 dollars: $141.7 billion
• Approx. cost to the U.S. during conflict: $61.0 billion
• Peak year of war spending during conflict: 1991 (0.3% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 694,550 troops
• Total battle deaths of U.S. service members: 148 fatalities
• Other deaths of U.S. service members associated with conflict: 235 fatalities
• American troops who suffered non-fatal wounds: 467 wounded

6. World War I (1917-1921)

• Approx. cost to the U.S. in 2025 dollars: $373.5 billion
• Approx. cost to the U.S. during conflict: $20.0 billion
• Peak year of war spending during conflict: 1919 (13.6% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 4,734,991 troops
• Total battle deaths of U.S. service members: 53,402 fatalities
• Other deaths of U.S. service members associated with conflict: 63,114 fatalities
• American troops who suffered non-fatal wounds: 204,002 wounded

5. Korean War (1950-1953)

• Approx. cost to the U.S. in 2025 dollars: $472.4 billion
• Approx. cost to the U.S. during conflict: $30.0 billion
• Peak year of war spending during conflict: 1952 (4.2% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 1,789,000 troops
• Total battle deaths of U.S. service members: 33,739 fatalities
• Other deaths of U.S. service members associated with conflict: 2,835 fatalities
• American troops who suffered non-fatal wounds: 103,284 wounded

4. Vietnam War (1965-1975)

• Approx. cost to the U.S. in 2025 dollars: $1.0 trillion
• Approx. cost to the U.S. during conflict: $111.0 billion
• Peak year of war spending during conflict: 1968 (2.3% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 3,403,000 troops
• Total battle deaths of U.S. service members: 47,434 fatalities
• Other deaths of U.S. service members associated with conflict: 10,786 fatalities
• American troops who suffered non-fatal wounds: 153,303 wounded

3. Afghanistan (Operations Enduring Freedom, Freedom’s Sentinel: 2001-2021)

• Approx. cost to the U.S. in 2025 dollars: $1.2 trillion
• Approx. cost to the U.S. during conflict: $849.8 billion
• Peak year of war spending during conflict: 2012 (0.6% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: N/A
• Total battle deaths of U.S. service members: 2,465 fatalities
• Other deaths of U.S. service members associated with conflict: N/A
• American troops who suffered non-fatal wounds: N/A

2. Iraq and Syria (Operations Iraqi Freedom, New Dawn, Inherent Resolve: 2003-2021)

• Approx. cost to the U.S. in 2025 dollars: $1.2 trillion
• Approx. cost to the U.S. during conflict: $616.0 billion
• Peak year of war spending during conflict: 2008 (0.9% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: N/A
• Total battle deaths of U.S. service members: 4,626 fatalities
• Other deaths of U.S. service members associated with conflict: N/A
• American troops who suffered non-fatal wounds: 32,292 wounded

1. World War II (1941-1945)

• Approx. cost to the U.S. in 2025 dollars: $6.1 trillion
• Approx. cost to the U.S. during conflict: $296.0 billion
• Peak year of war spending during conflict: 1945 (35.8% of U.S. GDP)
• Total U.S. service men and women deployed in conflict: 16,112,566 troops
• Total battle deaths of U.S. service members: 291,557 fatalities
• Other deaths of U.S. service members associated with conflict: 113,842 fatalities
• American troops who suffered non-fatal wounds: 670,846 wounded