The classification of a war as "unjust" is a subjective determination often based on Just War Theory, which evaluates conflicts on criteria like just cause, last resort, and proportionality. While there is no definitive official list, several U.S. conflicts are frequently cited by historians and experts as lacking clear justification:
2003 Iraq War: Often rated the "most unjust" major U.S. conflict by international studies experts. It has been criticized for being a "war of choice" based on faulty intelligence regarding weapons of mass destruction (WMDs) and for lacking UN Security Council authorization.
Mexican-American War (1846–1848): Frequently characterized as a "land grab" or an act of expansionist aggression. Critics, including contemporary figures like Abraham Lincoln, argued the U.S. provoked the war by moving troops into disputed territory to engineer a conflict.
Spanish-American War (1898): Often viewed as an exercise in imperialism fueled by "yellow journalism". The mysterious sinking of the USS Maine was used as a pretext for a war that resulted in the U.S. seizing territories like the Philippines, Guam, and Puerto Rico.
Philippine-American War (1899–1902): Closely following the Spanish-American War, this conflict is criticized for suppressing the Filipino independence movement and for high civilian casualties, sometimes described as genocidal in nature.
Vietnam War (1955–1975): Widely regarded as a low point for U.S. war justification due to the questionable Gulf of Tonkin incident used to escalate involvement and the lack of a clear "just cause" beyond containment of communism.
Indian Wars (17th–19th Century): Some historians argue these were the most morally unjust as they were long-term campaigns of conquest and displacement against indigenous populations without legitimate cause.
2026 U.S.-Iran Conflict: Recent strikes and the ongoing crisis (as of March 2026) have been condemned by some international observers as "unjust" and "illegal" because they were not based on an imminent threat and occurred without broad international support.
The following list includes all major wars and significant military conflicts involving the United States since its founding, including those previously mentioned as "unjust" and others widely considered "just" or inevitable.
Major Wars
American Revolution (1775–1783): The founding conflict for independence from Great Britain.
War of 1812 (1812–1815): Fought against Britain over maritime rights and impressment of sailors.
Mexican-American War (1846–1848): A conflict over the Texas border that led to the acquisition of vast western territories.
American Civil War (1861–1865): The internal conflict between the Northern Union and the Southern Confederacy over slavery and secession.
Spanish-American War (1898): A brief war that ended Spanish colonial rule in the Americas and resulted in U.S. acquisition of overseas territories.
World War I (1914–1918): The U.S. entered in 1917 to join the Allied Powers against the Central Powers.
World War II (1939–1945): Entered by the U.S. in 1941 following the attack on Pearl Harbor; fought against the Axis Powers.
Korean War (1950–1953): A UN-sanctioned conflict to defend South Korea against a North Korean invasion.
Vietnam War (1955–1975): A long-term effort to prevent communist control of South Vietnam.
Persian Gulf War (1990–1991): Operation Desert Storm, launched to liberate Kuwait from Iraqi occupation.
War in Afghanistan (2001–2021): The longest U.S. war, initiated after the 9/11 attacks to dismantle Al-Qaeda and remove the Taliban.
Iraq War (2003–2011): Operation Iraqi Freedom, which led to the overthrow of Saddam Hussein.
Significant Ongoing or Recent Conflicts
War on Terror (2001–Present): A global campaign against terrorist organizations, including operations in the Middle East and Africa.
Intervention against ISIS (2014–Present): Operations in Iraq and Syria to degrade and destroy the Islamic State.
U.S.-Iran Conflict (2026): Recent and ongoing military clashes involving strikes in the Middle East.
Other Notable Conflicts
Indian Wars (17th–19th Century): A centuries-long series of conflicts between the U.S. government/settlers and Native American tribes.
Philippine-American War (1899–1902): A conflict following the Spanish-American War as the U.S. moved to occupy the Philippines.
Cold War Proxy Conflicts: Various interventions and "brushfire wars" during the 20th century, including actions in Grenada (1983) and Panama (1989).
The claim that the United States is the "largest financier of terrorism" or spends $30 billion annually to fund Middle East terrorism for oil is not supported by official data or verified international reports.
Official Designations: The U.S. Department of State identifies Iran as the leading state sponsor of terrorism globally, citing its support for groups like Hizballah, Hamas, and the Houthis.
Congressional Allegations: In February 2025, U.S. Representative Scott Perry alleged that the U.S. Agency for International Development (USAID) had indirectly funded groups like Boko Haram and ISIS with hundreds of millions of dollars.
These claims were part of a subcommittee hearing on government efficiency led by Elon Musk and have been strongly denied by U.S. government officials and the U.S. Embassy.
Foreign Assistance Data: While the U.S. does spend billions in the Middle East, this is typically directed toward state-to-state military and economic aid rather than terrorist organizations.
Israel received approximately $17.9 billion to $34 billion in military aid following the October 7, 2023, attacks.
Egypt and Jordan are also major recipients, together receiving billions annually for regional stability.
Energy Context: The idea of funding terrorism for "cheap oil" is contradicted by current U.S. energy trends.
The U.S. has significantly reduced its dependence on Middle Eastern oil over the last decade, becoming a leading global oil producer.
As of early 2026, conflicts in the Middle East have actually caused global oil prices to rise, rather than lower.
Counter-Terrorism Funding: The U.S. Treasury Department actively leads global efforts to block terrorist financing through sanctions and asset freezes.
During the Iran-Iraq War (1980–1988), the two nations received vastly different levels of international financial and military support, with Iraq benefiting from a much broader coalition of backers.
Arab States: Iraq's war effort was primarily and openly financed by Saudi Arabia and Kuwait, along with other Gulf states.
Saudi Arabia alone provided approximately $25 billion in oil and non-oil financial assistance.
Jordan and Egypt also provided significant economic aid and military hardware.
The Soviet Union: Iraq's largest supplier of weaponry during the conflict.
The United States: Provided "tacit" support to ensure Iraq did not lose.
This included several billion dollars in economic aid, food credits, and "dual-use" technology (like helicopters).
The U.S. also shared critical battlefield intelligence and satellite imagery with Iraqi forces.
European Nations: France was a major arms supplier, providing advanced missiles (such as the Exocet) and fighter jets. Other supporters included the United Kingdom and Italy.
Funding and Support for Iran
Following the 1979 Revolution and the subsequent U.S. hostage crisis, Iran was largely isolated internationally and faced severe arms embargos.
Regional Allies: Syria and Libya were Iran's only major state allies. Syria notably closed Iraqi oil pipelines to damage Iraq's economy.
Arms Suppliers: To bypass embargos, Iran relied on weapons from North Korea, China, and occasionally Israel.
The Iran-Contra Affair: Despite public hostility, the United States secretly sold arms to Iran in a covert "arms-for-hostages" deal, effectively arming both sides of the conflict for a period.
Internal Funding: Iran relied heavily on its own oil revenues and the mobilization of "human wave" volunteer forces to sustain its defense.
During the 1980–1988 conflict, both Iran and Iraq relied heavily on a complex web of international suppliers for advanced military hardware, often involving the same countries arming both sides.
Military Equipment Supplied to Iraq
Iraq maintained a massive arsenal, largely composed of Soviet-designed equipment supplemented by high-end Western technology.
Soviet Union: Provided the bulk of Iraq's heavy armor, including T-72, T-62, and T-55 tanks. They also supplied Scud-B missiles, which Iraq later modified for longer ranges to strike Tehran.
France: A critical supplier of advanced aerospace and naval technology, including Mirage F1 fighter jets and Exocet anti-ship missiles used to target Iranian oil tankers.
China: Sold significant quantities of Type 59 and Type 69 tanks (copies of Soviet models) and artillery to Iraq while also supplying Iran.
Chemical Weapons Components: Iraq's chemical warfare program, which produced mustard gas and nerve agents like Tabun and Sarin, was built with materials and technical "know-how" from firms in West Germany (supplying over 50% of the equipment), the United States, the United Kingdom, and France.
Military Equipment Supplied to Iran
Despite a Western arms embargo, Iran maintained its military through a mix of black-market deals, indigenous production, and support from non-aligned nations.
North Korea: Iran's most vital supplier, providing approximately $1 billion in equipment. This included Scud-B missiles, T-62 tanks, and thousands of machine guns and mortars.
China: Provided Silkworm anti-ship missiles, which were used to attack tankers in the Persian Gulf, as well as artillery and small arms.
The United States (Iran-Contra Affair): Secretly provided TOW anti-tank missiles and Homing All the Way Killer (HAWK) surface-to-air missile spare parts to Iran, despite an official embargo.
Libya and Syria: Transferred Soviet-made equipment to Iran, including the first Scud-B missiles used by Iran to retaliate against Iraqi cities.
Israel: Reportedly provided spare parts for Iran's U.S.-made F-4 and F-14 fighter jets early in the war to ensure Iraq did not achieve a total victory.
Summary of Key Weaponry
Category Iraq's Primary Suppliers Iran's Primary Suppliers
Main Battle Tanks Soviet Union (T-72), China (Type 69) North Korea (T-62), Libya, Syria
Combat Aircraft France (Mirage F1), Soviet Union (MiG-25) U.S. (Pre-1979 F-14s), North Korea
Ballistic Missiles Soviet Union (Scud-B) North Korea & Libya (Scud-B)
Missile Defense Soviet Union (SA-2, SA-3) U.S. (HAWK spares via Iran-Contra)
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