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Richard Nixon conducted a secret bombing of Cambodia without Congressional approval in 1970.
Bettmann Archive/GettyImages
Both houses of Congress have advanced War Powers resolutions in the wake of the war with Iran.
Presidents have repeatedly ordered military operations without Congress since WWII.
In some instances, lawmakers have checked the president's power in response.
A week ago, the United States' and Israel's war against Iran passed the 100-day mark. In the more than three months since the war began, a host of ethical, economic, and political questions have arisen about the conflict.
One of the most pressing political questions has centered on the legality of the war itself. Operation Epic Fury, a large-scale military operation, was launched without congressional authorization, which lawmakers argue is required under the Constitution.
On June 3, the House of Representatives passed a War Powers resolution that, if passed by the Senate, would require the removal of all offensive forces within 30 days of its passage, per PBS News. In May, the Senate advanced its own resolution, which hasn't been brought to a final vote.
The House resolution will require 60 votes in the Senate in order to be brought to a vote. President Donald Trump would then hold the ability to veto the resolution, which would require a two-thirds vote from both houses to override it.
In May, Trump argued that a ceasefire with Iran meant hostilities were "terminated" and therefore congressional approval wasn't necessary. Since Trump's comments, the US has carried out further strikes against Iran, which government officials labeled "self-defense" strikes, PBS News reported.
Congress hasn't officially declared war since June 4, 1942, when it declared war on Bulgaria, Hungary, and Romania during World War II. Since then, in instances like the Gulf War, the war in Afghanistan, and the Iraq War, Congress has typically approved force via "Authorization for Use of Military Force." While not an official declaration of war, it allows the military to engage in targeted objectives, according to the Library of Congress.
Still, there have been plenty of times throughout American history when the president has ordered large-scale military operations without direct congressional approval, whether through loose interpretations of presidential powers or without providing any legal justification.
While this practice has been met with legal challenges at times, in other instances, presidents have avoided scrutiny from Congress due to widespread support for the military action.
Andrew Wiest, a professor of military history at the University of Southern Mississippi, said these instances are part of a broader concession of Congressional war powers to the executive branch since WWII.
"Since 1946, Congress has relinquished this constitutional authority and granted it to the president, probably much to the founders' chagrin," Wiest said. "The founders were extremely wary of a president with too much military authority."
Here are 11 notable examples of US military operations conducted without direct congressional approval.
Philippine-American War
American soldiers in the Philippines during the Philippine-American War, May 1899.
Hulton Archive/Getty Images
Even before WWII, certain US military actions were the source of fierce debate. Following the Spanish-American War, the Philippine Islands were ceded to the US in the Treaty of Paris in 1898. Despite the United States' claim to the territory, Filipino revolutionary fighters declared independence and resisted American attempts to acquire the islands.
President William McKinley never sought a formal declaration of war or authorization from Congress. Since the Treaty of Paris was newly ratified by Congress, however, McKinley interpreted it as an effective approval of force from lawmakers. The war was controversial in Congress, with anti-imperialists claiming the annexation of the Philippines was illegal, according to the House of Representatives.
The war lasted over three years, from 1899 to 1902, and American deaths totaled 4,200. About 20,000 Filipino fighters were killed, while up to 200,000 civilians died of disease, famine, and violence, per the Department of State.
Korean War
American soldiers in the Korean War. President Truman labeled the effort a "police action."
Keystone/Getty Images
After the US and Soviet Union divided Korea into two countries following WWII, fighting ensued in 1950 when North Korean forces invaded South Korea. The United Nations Security Council soon directed its member nations to assist South Korea, prompting US involvement.
President Harry Truman, however, never sought any form of approval from Congress, instead labeling the US's efforts a "police action" under the auspices of the UN. This framing was refuted by some members of Congress, with Republican Senator Robert Taft claiming the lack of congressional approval was "a complete usurpation by the president of authority to use the armed forces of this country," per the Brennan Center.
The war's identity as an international effort overshadowed the lack of congressional approval, according to Wiest.
"At the time, the UN was young, robust, and something new," Wiest said. "With a UN resolution to defend South Korea, what more top cover do you need?"
The Korean War ultimately lasted three years and resulted in the deaths of 37,000 American soldiers, according to the Department of Defense. As many as 5 million people lost their lives in total from the conflict, many of them civilians.
Vietnam War
American soldiers of the 173th airborne are evacuated by helicopter from a Vietcong position in December 1965.
AFP via Getty Images
Congress passed the Gulf of Tonkin Resolution in August 1964, giving President Lyndon Johnson the authority to use military force in Vietnam and the surrounding countries. But as the war dragged on and opposition at home grew, pressure mounted on the US government, and questions arose about Johnson's continued war powers.
Then, two years after Richard Nixon had assumed office, Congress repealed the resolution, meaning no law on the books authorized US military force in Southeast Asia. Though Nixon began reducing the number of deployed US troops when he took office in 1969, bombing campaigns continued until the end of the war.
A federal appeals court later declared the war a political issue and did not rule on the legality of Nixon's continued bombing, The New York Times reported.
A total of 58,220 Americans died as a result of the war, per the National Archives.
Bombing of Cambodia
The aftermath of a US B-52 bombing in Phnom Penh, Cambodia. Congress later passed the War Powers Resolution of 1973, limiting Nixon's military power.
Bettman Archive/GettyImages
Nixon also conducted bombing campaigns in Cambodia, which began in 1969 and continued after the repeal of the Gulf of Tonkin resolution. The operation — to disrupt supply routes along the Ho Chi Minh trail and to target suspected communist hubs — began in secret without Congress ever being informed.
The bombings prompted Congress' passing of the War Powers Resolution of 1973, which aimed to limit the president's power in conducting military operations. Nixon vetoed the legislation, but Congress overrode the veto with a two-thirds majority.
The successful war-powers challenge represented a rare moment in modern American history where Congress reclaimed its war powers. Wiest said political factors play a large role in Congress' usual inaction.
"Partisanship and politics is part of it," Wiest said. "No congressman can be seen as being against the troops. In my view, there's no more risky electoral thing to do."
From 1969 to 1973, the US dropped 540,000 tons of bombs on Cambodia. Estimates for civilians killed as a result of the bombings range from 150,000 to 500,000, per PBS Frontline.
1983 invasion of Grenada
US soldiers run across a soccer field during the US invasion of Grenada in October 1983.
Bettmann Archive/Getty Images
In 1983, a coup in Grenada resulted in the execution of the country's leader, Maurice Bishop. Ostensibly to protect hundreds of medical students in the country and restore order after the government's overthrow, the US invaded the island nation with help from Caribbean allies.
The US invasion, ordered by President Ronald Reagan, was carried out without congressional approval. This prompted Congress to apply the War Powers Resolution, forcing withdrawal of US troops within 60 days, The New York Times reported.
The campaign only lasted eight days, but it resulted in the death of 19 US soldiers and 24 Grenadian civilians, per Army University Press.
1989 invasion of Panama
US soldiers inspect a prison cell in Panama during the 1989 invasion.
Steven D Starr/Corbis via Getty Images
In what was codenamed Operation Just Cause, the US invaded Panama in 1989 with the intention of overthrowing its leader, Manuel Noriega, who was indicted under US law for drug trafficking.
Other reasons cited for the operation were protecting Americans in Panama, defending democracy, and protecting the Panama Canal treaties. The State Department said the actions were also carried out with the consent of Panama's legitimate government, which was sworn in before the invasion.
Like Reagan before him, President George H.W. Bush didn't seek congressional approval beforehand. However, the invasion had strong public and congressional support, subduing potential war-powers challenges.
The invasion was swift, and Noriega was quickly captured and tried in the US. He was later convicted and sentenced to 40 years in prison, eventually serving 17 years in the US.
All in all, 23 US soldiers were killed in the operation, and an internal US Army memo estimated the number of Panamanian deaths at around 1,000, per Politico.
1999 NATO bombing of Yugoslavia
A Kosovan civilian in Pec, Yugoslavia walks among rubble in June 1999.
Georges MERILLON/Gamma-Rapho via Getty Images
During the Kosovo War, NATO forces led by the US initiated a bombing campaign in Yugoslavia against the Yugoslav Army.
NATO said the strikes were intended to stop "ethnic cleansing" of Kosovar Albanians by Yugoslav forces and to pressure those forces to leave Kosovo.
Though Congress originally voted to send US peacekeeping troops to NATO in March of 1999 before the bombing began, a later House measure authorizing the strikes failed in a tie vote.
The continued bombing campaign under President Bill Clinton later prompted a war powers lawsuit filed by 31 members of the House, which was dismissed by a judge on the grounds that "a clear impasse between the executive and legislative branches" was absent, CBS News reported.
Much as with the Korean War after WWII, Wiest said, the notion of internationalism following the end of the Cold War provided cover for the operation's legality.
"It was a period of early optimism in the wake of a world-changing event, so that optimism, with the top cover of the UN or NATO, just overwhelmed any American constitutional need to declare war," he said.
As well as killing over 1,000 Yugoslav combatants, the strikes claimed the lives of roughly 500 civilians, per Human Rights Watch.
2011 US and NATO intervention in Libya
A missile being fired from the USS Barry during operation Odyssey Dawn.
DDG 52/GettyImages
As part of an intervention conducted by NATO forces, US forces participated in strikes on Libya during the Libyan Civil War. In response to Libyan leader Muammar Gaddafi's attacks on civilians, the United Nations Security Council adopted Resolution 1973 on March 17, 2011, which authorized military action in Libya.
President Barack Obama never sought congressional approval for the action, leading to criticism from Congress and 10 House members filing a lawsuit in an attempt to block further military action, NPR reported.
The legal action was later dismissed by a federal judge, Reggie Walton, who noted that lawmakers already had the legislative means to challenge the military operation in Congress. In light of other pressing political issues, Walton said, "…the Court finds it frustrating to expend time and effort adjudicating the relitigation of settled questions of law."
The Obama administration used the UN Security Council resolution as a justification and claimed the operation was limited and thus within the scope of the War Powers Resolution.
US strikes in Yemen
A Yemeni man walks among the rubble of a destroyed building.
AFP/GettyImages
The US struck Houthi targets in Yemen after the military group began targeting commercial ships in 2023 in response to Israel's invasion of the Gaza Strip.
Both the Biden and Trump administrations conducted strikes against the Houthis without seeking congressional approval. The most recent strikes in 2025, conducted by the Trump administration, killed at least 224 civilians, per the Middle East monitoring group Airwars.
Wiest said there's a double standard applied to ground versus air military operations, with the latter offering more war-powers leeway.
"The use of air power has almost been a kind of national 'Get Out of Jail Free' card when it comes to opening these types of conflicts," he said.
2025 strikes on Iran nuclear sites
B-2 spirit stealth bombers like the one pictured here over Afghanistan were used in Operation Midnight Hammer.
USAF/Getty Images
In what was codenamed Operation Midnight Hammer, the Trump administration struck Iran's nuclear facilities without Congressional approval. President Trump argued the strike was a necessary measure to prevent Iran from developing a nuclear weapon.
While the strikes had the broad support of Republican lawmakers, Democrats and Republican Thomas Massie criticized the operation's lack of authorization from Congress, NPR reported.
2026 US raid inside Venezuela
Venezuelan President Nicolas Maduro, and his wife, as they're escorted to court in Manhattan.
ADAM GRAY/REUTERS
On January 3, the Trump administration conducted surprise strikes on Venezuela that deposed the country's president, Nicolás Maduro. Maduro was captured and brought to the US, where he faces narco-terrorism and other drug charges. The former Venezuelan leader has pleaded not guilty.
The Trump administration justified the strikes by calling them "law-enforcement operations" to target what it called Maduro's "narco-terrorist organization."
The strikes resulted in about 75 deaths, including two civilians and 32 Cuban special forces, per the Center for Strategic & International Studies. Seven American troops were injured.
Critics in Congress questioned the legality of the intervention. While a war powers resolution was brought to the floor for a vote in the Senate, it was blocked by the Republican-led majority.
Editor's note: This story was originally published in March 2026. It was most recently updated in June 2026.
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