World War I, also known as the First World War, the Great War, or the War to End All Wars, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. More than 70 million military personnel, including 60 million Europeans, were mobilized in one of the largest wars in history. Over nine million combatants and seven million civilians died as a result of the war (including the victims of a number of genocides), a casualty rate exacerbated by the belligerents' technological and industrial sophistication, and the tactical stalemate caused by grueling trench warfare. It was one of the deadliest conflicts in history, and paved the way for major political changes, including revolutions in many of the nations involved and to the Second World War twenty-one years later. The war drew in all the world's economic great powers, assembled in two opposing alliances: the Allies (based on the Triple Entente of the Russian Empire, the French Third Republic, and the United Kingdom of Great Britain and Ireland) versus the Central Powers of Germany and Austria-Hungary. Although Italy was a member of the Triple Alliance alongside Germany and Austria-Hungary, it did not join the Central Powers, as Austria-Hungary had taken the offensive against the terms of the alliance. These alliances were reorganized and expanded as more nations entered the war: Italy, Japan and the United States joined the Allies, while the Ottoman Empire and Bulgaria joined the Central Powers. The trigger for the war was the assassination of Archduke Franz Ferdinand of Austria, heir to the throne of Austria-Hungary, by Yugoslav nationalist Gavrilo Princip in Sarajevo on 28 June 1914. This set off a diplomatic crisis when Austria-Hungary delivered an ultimatum to the Kingdom of Serbia, and entangled international alliances formed over the previous decades were invoked. Within weeks, the major powers were at war and the conflict soon spread around the world. On 25 July Russia began mobilization and on 28 July the Austro-Hungarians declared war on Serbia. Germany presented an ultimatum to Russia to demobilize, and when this was refused, declared war on Russia on 1 August. Being outnumbered on the Eastern Front, Russia urged its Triple Entente ally France to open up a second front in the west. Back in 1870, the Franco-Prussian War had ended the Second French Empire and ceded the provinces of Alsace-Lorraine to a unified Germany. Bitterness over that defeat and the determination to retake Alsace-Lorraine made the acceptance of Russia's plea for help an easy choice, so France began full mobilization on 1 August and, on 3 August, Germany declared war on France. The border between France and Germany was heavily fortified on both sides so according to the Schlieffen Plan, Germany then invaded neutral Belgium and Luxembourg before moving towards France from the north, leading the United Kingdom to declare war on Germany on 4 August due to their violation of Belgian neutrality.[12][13] After the German march on Paris was halted in the Battle of the Marne, what became known as the Western Front settled into a battle of attrition, with a trench line that changed little until 1917. On the Eastern Front, the Russian army led a successful campaign against the Austro-Hungarians, but the Germans stopped its invasion of East Prussia in the battles of Tannenberg and the Masurian Lakes. In November 1914, the Ottoman Empire joined the Central Powers, opening fronts in the Caucasus, Mesopotamia and the Sinai. In 1915, Italy joined the Allies and Bulgaria joined the Central Powers; Romania joined the Allies in 1916, as did the United States in 1917. The Russian government collapsed in March 1917, and a revolution in November followed by a further military defeat brought the Russians to terms with the Central Powers via the Treaty of Brest Litovsk, which granted the Germans a significant victory. After a stunning German offensive along the Western Front in the spring of 1918, the Allies rallied and drove back the Germans in a series of successful offensives. On 4 November 1918, the Austro-Hungarian empire agreed to an armistice, and Germany, which had its own trouble with revolutionaries, agreed to an armistice on 11 November 1918, ending the war in victory for the Allies. By the end of the war or soon after, the German Empire, Russian Empire, Austro-Hungarian Empire and the Ottoman Empire ceased to exist. National borders were redrawn, with several independent nations restored or created, and Germany's colonies were parceled out among the victors. During the Paris Peace Conference of 1919, the Big Four (Britain, France, the United States and Italy) imposed their terms in a series of treaties. The League of Nations was formed with the aim of preventing any repetition of such a conflict. This effort failed, and economic depression, renewed nationalism, weakened successor states, and feelings of humiliation (particularly in Germany) eventually contributed to the start of World War II 

 World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945, although related conflicts began earlier. It involved the vast majority of the world's countries—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, and directly involved more than 100 million people from over 30 countries. In a state of "total war", the major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, erasing the distinction between civilian and military resources. Marked by mass deaths of civilians, including the Holocaust (in which approximately 11 million people were killed) and the strategic bombing of industrial and population centers (in which approximately one million were killed, and which included the atomic bombings of Hiroshima and Nagasaki),]it resulted in an estimated 50 million to 85 million fatalities. These made World War II the deadliest conflict in human history. The Empire of Japan aimed to dominate Asia and the Pacific and was already at war with the Republic of China in 1937, but the world war is generally said to have begun on 1 September 1939[6] with the invasion of Poland by Nazi Germany and subsequent declarations of war on Germany by France and the United Kingdom. Supplied by the Soviet Union, from late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbors, Poland, Finland, Romania and the Baltic states. The war continued primarily between the European Axis powers and the coalition of the United Kingdom and the British Commonwealth, with campaigns including the North Africa and East Africa campaigns, the aerial Battle of Britain, the Blitz bombing campaign, the Balkan Campaign as well as the long-running Battle of the Atlantic. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history, which trapped the major part of the Axis military forces into a war of attrition. In December 1941, Japan attacked the United States and European colonies in the Pacific Ocean, and quickly conquered much of the Western Pacific. The Axis advance halted in 1942 when Japan lost the critical Battle of Midway, near Hawaii, and Germany was defeated in North Africa and then, decisively, at Stalingrad in the Soviet Union. In 1943, with a series of German defeats on the Eastern Front, the Allied invasion of Sicily and the Allied invasion of Italy which brought about Italian surrender, and Allied victories in the Pacific, the Axis lost the initiative and undertook strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained all its territorial losses and invaded Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in South Central China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands. The war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops and the subsequent German unconditional surrender on 8 May 1945. Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 August and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, and the Soviet Union's declaration of war on Japan and invasion of Manchuria, Japan surrendered on 15 August 1945. Thus, ended the war in Asia, cementing the total victory of the Allies. World War II altered the political alignment and social structure of the world. The United Nations (UN) was established to foster international co-operation and prevent future conflicts. The victorious great powers—the United States, the Soviet Union, China, the United Kingdom, and France—became the permanent members of the United Nations Security Council. The Soviet Union and the United States emerged as rival superpowers, setting the stage for the Cold War, which lasted for the next 46 years. Meanwhile, the influence of European great powers waned, while the decolonization of Asia and Africa began. Most countries whose industries had been damaged moved towards economic recovery. Political integration, especially in Europe, emerged as an effort to end pre-war enmities and to create a common identity.  

  The Korean War (in South Korean Hangul: 한국전쟁; Hanja: 韓國戰爭; RR: Hanguk Jeonjaeng, "Korean War"; in North Korean Chosŏn'gŭl: 조국해방전쟁; Hancha: 祖國解放戰爭; MR: Choguk haebang chǒnjaeng, "Fatherland Liberation War"; 25 June 1950 – 27 July 1953)[36][b][38] began when North Korea invaded South Korea.[39][40] The United Nations, with the United States as the principal force, came to the aid of South Korea. China came to the aid of North Korea, and the Soviet Union gave some assistance. Korea was ruled by Japan from 1910 until the closing days of World War II. In August 1945, the Soviet Union declared war on Japan, as a result of an agreement with the United States, and liberated Korea north of the 38th parallel. U.S. forces subsequently moved into the south. By 1948, as a product of the Cold War between the Soviet Union and the United States, Korea was split into two regions, with separate governments. Both claimed to be the legitimate government of all of Korea, and neither accepted the border as permanent. The conflict escalated into open warfare when North Korean forces—supported by the Soviet Union and China—moved into the south on 25 June 1950.On 27 June, the United Nations Security Council authorized the formation and dispatch of UN forces to Korea to repel what was recognized as a North Korean invasion.Twenty-one countries of the United Nations eventually contributed to the UN force, with the United States providing 88% of the UN's military personnel. After the first two months of war, South Korean and American forces rapidly dispatched to Korea were on the point of defeat, forced back to a small area in the south known as the Pusan Perimeter. In September 1950, an amphibious UN counter-offensive was launched at Inchon, and cut off many North Korean troops. Those who escaped envelopment and capture were forced back north. UN forces rapidly approached the Yalu River—the border with China—but in October 1950, mass Chinese forces crossed the Yalu and entered the war.The surprise Chinese intervention triggered a retreat of UN forces which continued until mid-1951. After these reversals of fortune, which saw Seoul change hands four times, the last two years of fighting became a war of attrition, with the front line close to the 38th parallel. The war in the air, however, was never a stalemate. North Korea was subject to a massive bombing campaign. Jet fighters confronted each other in air-to-air combat for the first time in history, and Soviet pilots covertly flew in defense of their communist allies. The fighting ended on 27 July 1953, when an armistice was signed. The agreement created the Korean Demilitarized Zone to separate North and South Korea, and allowed the return of prisoners. However, no peace treaty has been signed, and the two Koreas are technically still at war.[43][44] As a war undeclared by all participants, the conflict helped bring the term "police action" into common use. It also led to the permanent alteration of the balance of power within the United Nations, where Resolution 377—passed in 1950 to allow a bypassing of the Security Council if that body could not reach an agreement—led to the General Assembly displacing the Security Council as the primary organ of the UN


    The Vietnam War (Vietnamese: Chiến tranh Việt Nam), also known as the Second Indochina War, and known in Vietnam as Resistance War Against America (Vietnamese: Kháng chiến chống Mỹ) or simply the American War, was a war that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vietnam and the government of South Vietnam. The North Vietnamese army was supported by the Soviet Union, China and other communist allies and the South Vietnamese army was supported by the United States, South Korea, Australia, Thailand and other anti-communist allies. The war is therefore considered a Cold War-era proxy war. The Viet Cong (also known as the National Liberation Front, or NLF), a South Vietnamese communist common front aided by the North, fought a guerrilla war against anti-communist forces in the region, while the People's Army of Vietnam, also known as the North Vietnamese Army (NVA), engaged in more conventional warfare, at times committing large units to battle. As the war continued, the military actions of the Viet Cong decreased as the role and engagement of the NVA grew. U.S. and South Vietnamese forces relied on air superiority and overwhelming firepower to conduct search and destroy operations, involving ground forces, artillery, and airstrikes. During the war, the U.S. conducted a large-scale strategic bombing campaign against North Vietnam. The North Vietnamese government and the Viet Cong were fighting to reunify Vietnam. They viewed the conflict as a colonial war and a continuation of the First Indochina War against forces from France and later on the United States. The U.S. government viewed its involvement in the war to prevent a communist takeover of South Vietnam. This was part of the domino theory of a wider containment policy, with the stated aim of stopping the spread of communism worldwide. Beginning in 1950, American military advisors arrived in what was then French Indochina. U.S. involvement escalated in the early 1960s, with troop levels tripling in 1961 and again in 1962.[61] U.S. involvement escalated further following the 1964 Gulf of Tonkin incident, in which a U.S. destroyer clashed with North Vietnamese fast attack craft, which was followed by the Gulf of Tonkin Resolution, which gave the U.S. president authorization to increase U.S. military presence. Regular U.S. combat units were deployed beginning in 1965. Operations crossed international borders: bordering areas of Laos and Cambodia were heavily bombed by U.S. forces as American involvement in the war peaked in 1968, the same year that the communist side launched the Tet Offensive. The Tet Offensive failed in its goal of overthrowing the South Vietnamese government, but became the turning point in the war, as it persuaded a large segment of the U.S. population that its government's claims of progress toward winning the war were illusory despite many years of massive U.S. military aid to South Vietnam. Gradual withdrawal of U.S. ground forces began as part of "Vietnamization", which aimed to end American involvement in the war while transferring the task of fighting the communists to the South Vietnamese themselves. Despite the Paris Peace Accord, which was signed by all parties in January 1973, the fighting continued. In the U.S. and the Western world, a large anti-Vietnam War movement developed as part of a larger counterculture. The war changed the dynamics between the Eastern and Western Blocs, and altered North–South relations. Direct U.S. military involvement ended on 15 August 1973. The capture of Saigon by the North Vietnamese Army in April 1975 marked the end of the war, and North and South Vietnam were reunified the following year. The war exacted a huge human cost in terms of fatalities (see Vietnam War casualties). Estimates of the number of Vietnamese soldiers and civilians killed vary from 966,000 to 3.8 million. Some 240,000–300,000 Cambodians, 20,000–62,000 Laotians, and 58,220 U.S. service members also died in the conflict, and a further 1,626 remain missing in action.  



  The Iraq War was a protracted armed conflict that began in 2003 with the invasion of Iraq by a United States-led coalition that toppled the government of Saddam Hussein. The conflict continued for much of the next decade as an insurgency emerged to oppose the occupying forces and the post-invasion Iraqi government. An estimated 151,000 to 600,000 or more Iraqis were killed in the first 3–4 years of conflict. The U.S. became re-involved in 2014 at the head of a new coalition; the insurgency and many dimensions of the civil armed conflict continue. The invasion occurred in the context of a declared war against international terrorism and its sponsors under the administration of US President George W. Bush following the September 11 terror attacks. The invasion began on 20 March 2003, with the U.S., joined by the United Kingdom and several coalition allies, launching a "shock and awe" bombing campaign. Iraqi forces were quickly overwhelmed as U.S. forces swept through the country. The invasion led to the collapse of the Ba'athist government; President Hussein was captured during Operation Red Dawn in December of that same year and executed by a military court three years later. However, the power vacuum following Saddam's demise and the mismanagement of the occupation led to widespread sectarian violence between Shias and Sunnis, as well as a lengthy insurgency against U.S. and coalition forces. Many violent insurgent groups were supported by Iran and al-Qaeda in Iraq. The United States responded with a troop surge in 2007. The winding down of U.S. involvement in Iraq accelerated under President Barack Obama. The U.S. formally withdrew all combat troops from Iraq by December 2011. The Bush administration based its rationale for the war principally on the assertion that Iraq, which had been viewed as a rogue state since the Persian Gulf War, possessed weapons of mass destruction (WMDs) and that the Iraqi government posed an immediate threat to the United States and its coalition allies. Select U.S. officials accused Saddam of harboring and supporting al-Qaeda, while others cited the desire to end a repressive dictatorship and bring democracy to the people of Iraq. After the invasion, no substantial evidence was found to verify the initial claims about WMDs, while claims of Iraqi officials collaborating with al-Qaeda were proven false. The rationale and misrepresentation of US prewar intelligence faced heavy criticism both domestically and internationally, with President Bush declining from his record-high approval ratings following 9/11 to become one of the most unpopular presidents in US history. In the aftermath of the invasion, Iraq held multi-party elections 2005. Nouri al-Maliki became Prime Minister in 2006 and remained in office until 2014. The al-Maliki government enacted policies that were widely seen as having the effect of alienating the country's Sunni minority and worsening sectarian tensions. In the summer of 2014, the Islamic State of Iraq and the Levant (ISIL) launched a military offensive in Northern Iraq and declared a worldwide Islamic caliphate, eliciting another military response from the United States and its allies. The Iraq War caused hundreds of thousands of civilian, and thousands of military casualties (see estimates below). The majority of casualties occurred as a result of the insurgency and civil conflicts between 2004 and 2007.  

  The War in Afghanistan (or the U.S. War in Afghanistan)followed the 2001 United States invasion of Afghanistan. The U.S. was supported initially by Canada] and the United Kingdom and later by a coalition of over 40 countries including all NATO members under a United Nations mandate. The war's public aims were to dismantle al-Qaeda and to deny it a safe base of operations in Afghanistan by removing the Taliban from power. The War in Afghanistan is the longest war in United States history. Following the September 11 attacks in 2001, U.S. President George W. Bush demanded that the Taliban hand over Osama bin Laden and expel al-Qaeda; bin Laden had already been wanted by the U.S. since 1998. The Taliban declined to extradite him unless given evidence of his involvement in the September 11 attacks and also declined demands to extradite others on the same grounds. The U.S. dismissed the request for evidence as a delaying tactic,] and on 7 October 2001 launched Operation Enduring Freedom with the United Kingdom. The two were later joined by other forces, including the Northern Alliance which had been fighting the Taliban in the ongoing civil war since 1996. In December 2001, the United Nations Security Council established the International Security Assistance Force (ISAF), to assist the Afghan interim authorities with securing Kabul. At the Bonn Conference the same month, Hamid Karzai was selected to head the Afghan Interim Administration, which after a 2002 loya jirga (grand assembly) in Kabul became the Afghan Transitional Administration. In the popular elections of 2004, Karzai was elected president of the country, now named the Islamic Republic of Afghanistan. NATO became involved in ISAF in August 2003, and later that year assumed leadership of it. At this stage, ISAF included troops from 43 countries with NATO members providing the majority of the force. One portion of U.S. forces in Afghanistan operated under NATO command; the rest remained under direct U.S. command. Following defeat in the initial invasion, the Taliban was reorganized by its leader Mullah Omar, and launched an insurgency against the government and ISAF in 2003.Though outgunned and outnumbered, insurgents from the Taliban, Haqqani Network, Hezb-e-Islami Gulbuddin and other groups have waged asymmetric warfare with guerilla raids and ambushes in the countryside, suicide attacks against urban targets and turncoat killings against coalition forces. The Taliban exploited weaknesses in the Afghan government, which is among the most corrupt in the world, to reassert influence across rural areas of southern and eastern Afghanistan. In the initial years there was little fighting, but from 2006 the Taliban made significant gains and showed an increased willingness to commit atrocities against civilians. ISAF responded in 2006 by increasing troops for counterinsurgency operations to "clear and hold" villages and "nation building" projects to "win hearts and minds". Violence sharply escalated from 2007 to 2009.While ISAF continued to battle the Taliban insurgency, fighting crossed into neighboring North-West Pakistan.Troop numbers began to surge in 2009 continued to increase through 2011 when roughly 140,000 foreign troops operated under ISAF and U.S. command in Afghanistan. Of these 100,000 were from the U.S On 1 May 2011, United States Navy SEALs killed Osama bin Laden in Abbotabad, Pakistan. In May 2012, NATO leaders endorsed an exit strategy for withdrawing their forces. UN-backed peace talks have since taken place between the Afghan government and the Taliban. In May 2014, the United States announced that its major combat operations would end in December 2014, and that it would leave a residual force in the country.[65] In October 2014, British forces handed over the last bases in Helmand to the Afghan military, officially ending their combat operations in the war. On 28 December 2014, NATO formally ended ISAF combat operations in Afghanistan and officially transferred full security responsibility to the Afghan government. The NATO led Operation Resolute Support was formed the same day as a successor to ISAF. In May 2017, over 13,000 foreign troops remain in Afghanistan without any formal plans to withdraw. Tens of thousands of people have been killed in the war. Over 4,000 ISAF soldiers and civilian contractors, over 15,000 Afghan national security forces were killed, as well as over 31,000 civilians.