Query: Societies do fall apart from war, disease or chaos.

Relevant passages:
Vietnam War <=SEP=> The Vietnam War ( Chiến tranh Việt Nam ) , also known as the Second Indochina War , and known in Vietnam as Resistance War Against America ( 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 . In the course of 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 as a way 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.The Military Assistance Advisory Group , Indochina ( with an authorized strength of 128 men ) was set up in September 1950 with a mission to oversee the use and distribution of US military equipment by the French and their allies . U.S. involvement escalated in the early 1960s , with troop levels tripling in 1961 and again in 1962 . 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 .

Apocalyptic and post-apocalyptic fiction <=SEP=> Apocalyptic and post-apocalyptic fiction is a subgenre of science fiction , science fantasy or horror fiction literature in which the Earth 's technological civilization is collapsing or has collapsed . The apocalypse event may be climatic , such as runaway climate change ; natural , such as an impact event ; man-made , such as nuclear warfare ; medical , such as a plague or virus , whether natural or man-made ; or imaginative , such as zombie apocalypse or alien invasion . The story may involve attempts to prevent an apocalypse event , deal with the impact and consequences of the event itself , or it may be post-apocalyptic , set after the event . The time frame may be immediately after the catastrophe , focusing on the travails or psychology of survivors , the way to maintain the human race alive and together as one , or considerably later , often including the theme that the existence of pre-catastrophe civilization has been forgotten ( or mythologized ) . Post-apocalyptic stories often take place in a non-technological future world , or a world where only scattered elements of society and technology remain .   Various ancient societies , including the Babylonian and Judaic , produced apocalyptic literature and mythology which dealt with the end of the world and of human society , such as the Epic of Gilgamesh , written ca. 2000 -- 1500 BC . And recognizable modern apocalyptic novels had existed since at least the first quarter of the 19th century , when Mary Shelley 's The Last Man ( 1826 ) was published . However , this form of literature gained widespread popularity after World War II , when the possibility of global annihilation by nuclear weapons entered the public consciousness .   As shown above , the apocalypse is also depicted in visual art , for example in Albert Goodwin 's painting Apocalypse ( 1903 ) .

American Civil War <=SEP=> The American Civil War was fought in the United States from 1861 to 1865 . After a long standing controversy over slavery and state 's rights , war broke out in April 1861 , when Confederates attacked Fort Sumter in South Carolina , shortly after Abraham Lincoln was elected . The nationalists of the Union proclaimed loyalty to the U.S. Constitution . They faced secessionists of the Confederate States of America advocating states ' rights to perpetual slavery and its expansion in the Americas .   Among the 34 U.S. states in February 1861 , seven Southern slave states individually declared their secession from the U.S. to form the Confederate States of America . The Confederacy grew to include eleven states ; it claimed two more border states ( Kentucky and Missouri ) , the Indian Territory , and the southern portions of the Union 's western territories of Arizona and New Mexico , which was organized and incorporated into the Confederacy as Confederate Arizona . The Confederacy was never diplomatically recognized by the United States government , nor was it recognized by any foreign country ( although Britain and France granted it belligerent status ) . The states that remained loyal , including the border states where slavery was legal , were known as the Union or the North .   The North and South quickly raised volunteer and conscription armies that fought mostly in the South over four years . During this time many innovations in warfare occurred , including the development and use of iron-clad ships , ultimately changing naval strategy around the world . The Union finally won the war when General Robert E. Lee surrendered to General Ulysses S. Grant at the battle of Appomattox , which triggered a series of surrenders by Confederate generals throughout the southern states . Four years of intense combat left 620,000 to 750,000 soldiers dead , a higher number than the number of American military deaths in World War I and World War II combined , and much of the South 's infrastructure was destroyed . The Confederacy collapsed , slavery was abolished and 4 million slaves were freed . The Reconstruction Era ( 1863 -- 1877 ) overlapped and followed the war , with the process of restoring national unity , strengthening the national government , and granting civil rights to freed slaves throughout the country . The Civil War is arguably the most studied and written about episode in American history .

World War I <=SEP=> World War I ( WWI or WW1 ) , 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 mobilised 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 gruelling 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 WWII 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 reorganised 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 mobilisation and on 28 July , the Austro-Hungarians declared war on Serbia . Germany presented an ultimatum to Russia to demobilise , 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 their defeat and the determinance to retake Alsace-Lorraine made the acceptance of Russia 's plea for help an easy choice so France began full mobilisation 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 . 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 .