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War is generally defined as a violent conflict between states or nations. It has shaped humanity's history, its social and political institutions, its values, and ideas. In the 18th century, America had to fight for its independence, engaging in a war that subsequently defined the nation and prompted the signing of the Declaration of Independence in 1776. Since then, the United States of America has become embroiled in some of the world's most destructive and controversial conflicts.
To learn about the wars the US has gotten involved in and why, including the recent conflict in Yemen, click through the gallery.
The Houthis are a militia group of approximately 20,000 fighters battling for control in Yemen. They were founded in the 1980s to oppose the influence neighboring Saudi Arabia held over their country, mainly through Yemen’s cruel and corrupt leader of more than 20 years, Ali Abdullah Saleh.
A devastating revolutionary war broke out in 2012 and claimed hundreds of thousands of lives until a ceasefire brought a decline in the violence in 2021. Over the years, the Houthis have taken control of much of Yemen’s west coast, which lies along the Red Sea. The Red Sea is one of the busiest shipping channels in the world, located not far from the all-important Suez Canal.
Following the outbreak of war in Gaza in October 2023, the Houthis came out in support of Hamas and began launching attacks on ships passing through the Red Sea along the coast of Yemen, targeting those associated with Israel and its allies. The majority of the missiles they launched were intercepted by countermeasures from the US and Israel. However, the situation has continued to escalate in recent months. This prompted the launch of a US-led military operation named Operation Prosperity Guardian in December.
On December 31, the US engaged in direct confrontation with the Houthis for the first time, killing 10 members of the group. Both Britain and the US have been shooting down drones and missiles launched. On January 11, President Joe Biden announced that he had ordered strikes on a number of targets in Yemen, with the support of several other countries in the coalition including the UK, Canada, Australia, and the Netherlands. Biden added that he will “not hesitate to direct further measures to protect our people and the free flow of international commerce as necessary.”
The American Revolutionary War was an insurrection by Patriots in the 13 colonies against British rule.
The war followed more than a decade of growing estrangement between the British crown and a large and influential segment of its North American colonies. Issues like taxation without representation and a slew of trade restrictions further fueled resentment towards the British.
Ultimately, the Taxation Acts, the Boston Massacre, the Boston Tea Party, and the Intolerable Acts were the four main causes that lead to the American Revolution. The American colonies sought independence from British rule, and fighting began on April 19, 1775, at the Battles of Lexington and Concord.
Twenty-nine years later, the British and the Americans were again at odds with each other, primarily over British violations of US maritime rights.
Compounding the issue was America's desire to expand settlement into Indian, British, and Spanish territories. Britain's aiding Native American tribes in their attacks on American citizens on the frontier only heightened the ill feelings between the two nations.
In the end, Congress, for the first time in American history, declared war on a foreign power. On June 18, 1812, the first shots were fired. The conflict ultimately ended in a draw on the battlefield.
The Mexican–American War started as a result the United States' annexation of Texas in 1845 and Mexico's refusal to recognize Texan independence.
Also propelling the two countries towards conflict was the dispute over the boundary between the United States and Texas on the Nueces Strip. Mexico's concerns over American expansion westward further stoked the fire.
On May 13, 1846, the United States Congress declared war on Mexico. The conflict resulted in the United States' acquisition of more than 1,300,000 sq km (500,000 sq mi) of Mexican territory extending westward from the Rio Grande to the Pacific Ocean.
The primary reason for the American Civil War was the decades of simmering tensions between northern and southern states over slavery.
The uncompromising differences between the free and slave states and Abraham Lincoln's pledge to keep slavery out of the territories resulted in 11 states seceding from the Union to form the Confederate States of America.
Civil war broke out on April 12, 1861. The North's goal in the beginning was preservation of the Union, not emancipation. However, the Emancipation Proclamation and Thirteenth Amendment brought about by the conflict were important milestones in the long process of ending legal slavery in the United States.
The Spanish–American War effectively began on April 25, 1898, when the United States declared war on Spain following the sinking of the Battleship Maine in Havana harbor in February, which was blamed on Spanish forces.
America had financial as well as trade interests in Cuba. The war with Spain served to protect American citizens and businesses in Cuba.
The short but decisive conflict led to the United States emerging predominant in the Caribbean region, and resulted in US acquisition of Puerto Rico, Guam, and the Philippines. Pictured are "Teddy's Colts," led by Theodore Roosevelt, after the July 1 Battle of San Juan Hill in Cuba.
The sinking of the RMS Lusitania on May 7, 1915, by a German U-boat was a major factor in building American support for a war. But it was Germany's resumption of submarine attacks on passenger and merchant ships in 1917 that became the primary motivation behind President Woodrow Wilson's decision to lead the United States into the First World War.
The Great War was the first time in American history that the United States sent soldiers abroad to defend foreign soil. The first American troops arrived in Europe in June 1917.
The United States sustained more than 320,000 casualties during WWI, including over 53,000 killed in action, over 63,000 non-combat related deaths, and 204,000 wounded.
On December 7, 1941, the Imperial Japanese Navy launched an unprovoked attack on the US naval base at Pearl Harbor in Honolulu, Hawaii. The United States was a neutral country at the time.
The following day, President Franklin Roosevelt delivered his "Day of Infamy Speech." Immediately afterwards, Congress declared war on Japan, and the United States entered the Second World War.
The United States ended the war in the Pacific in August 1945 by dropping atomic bombs over the Japanese cities of Hiroshima and Nagasaki, thus bringing to a close the most destructive military conflict in human history.
The Korean War was fought between North Korea and South Korea from 1950 to 1953. It began on June 25, 1950, when some 75,000 soldiers from the North Korean People's Army poured across the 38th parallel.
The United States intervened shortly afterwards, seizing the opportunity to defend a non-communist government from invasion by communist troops.
In 1953, North Korea, China, and the United States signed an armistice agreement. South Korea refused to do so, and also declined to validate a formal peace treaty. As such, the two Koreas remain technically at war.
Though the Vietnam War had started 10 years previously, in 1955, the US only became fully involved in 1965. On March 8 of that year, United States Marines came ashore at Da Nang as the first wave of US combat troops into South Vietnam, adding to the 25,000 US military advisers already in place.
The United States entered Vietnam with the principal purpose of preventing a communist takeover of the region.
Washington ultimately failed in its efforts to stem a communist takeover in South Vietnam: the two Vietnams were united under a communist banner in July 1976. Neighboring Laos and Cambodia similarly fell to communists. Over 58,000 American military personnel perished in the conflict.
The Gulf War was triggered by Iraq's invasion of Kuwait on August 2, 1990. Saddam Hussein's illegal and unjustified action prompted an immediate multilateral response.
The United States led an international coalition of 42 countries deployed to the region to fight against Iraq.
Iraqi forces were decimated in the fighting, and Kuwait was declared completely free of occupying troops on February 28, 1991.
However, instability in the region and a suspicion that Saddam Hussein was building up stockpiles of weapons of mass destruction (WMD) prompted US and allied forces to invade Iraq in March 2003.
America's goal was ostensibly the wholesale destruction of WMD and to end the dictatorship of Saddam Hussein.
The protracted conflict lasted eight years and, while Saddam Hussein's brutal regime was toppled, no WMD were found. It is estimated that 461,000 people died in Iraq from war-related causes between 2003 and 2011. The entire endeavor cost America US$3 trillion.
Sources: (History) (BBC) (Library of Congress)
See also: History's silliest excuses for war
Official reasons why the US has gone to war
An account of the many conflicts involving the US
LIFESTYLE Conflict
War is generally defined as a violent conflict between states or nations. It has shaped humanity's history, its social and political institutions, its values, and ideas. In the 18th century, America had to fight for its independence, engaging in a war that subsequently defined the nation and prompted the signing of the Declaration of Independence in 1776. Since then, the United States of America has become embroiled in some of the world's most destructive and controversial conflicts.
To learn about the wars the US has gotten involved in and why, including the recent conflict in Yemen, click through the gallery.