Why?

In four short years, from 1914 to 1918, over 10 million men and women serving in armed forces on fronts around the world were killed, while double that number were wounded, disabled and disfigured; and at least another 7 million civilians lost their lives as well. Most died horrific deaths. But as time passes by we tend to forget, a century later, how many sacrifices were made day after day on both sides of one the most deadly conflicts in human history. Civilized Productions has produced a wonderful choral album, Sacrifice and Solace, which features an octet called the Toronto Valour Ensemble who sang these carefully selected and uniquely composed songs from that era. It is available on CD Baby. The simple translation of the Arabic word "jihad" is struggle.

The Struggle Among Family

In 1865, after four bloody confusing years, the northern forces of the Union defeated the southern forces of the Confederacy, ending a so-called civil war that had pitted brother against brother and, with the states finally united, expansion westward was soon a matter of American policy. Recognizing the opportunities on many levels provided by a growing nation and a productive people, businesses in this ruthless era swallowed their competitors and politicians astutely noted the benefit of continued geographic expansion, whether by force or negotiation. 
In March 1867, Queen Victoria provided Royal Assent to the British North America Act and several months later the Dominion of Canada was created, and many Europeans bought tickets to find refuge in a vast and underpopulated country - notwithstanding the issue of land ownership still in dispute across the western provinces. So, nearly two decades later in 1885, to control their fertile prairies, to feed their growing empire, British soldiers quashed angry rebels in Saskatchewan and, to solidify its authority, the new Government of Canada then hanged opposing Metis and Native leaders.
Prosperity assured and the last spike driven, a decade would pass before Canadians would be sought to fight against Dutch and African farmers during the Second Boer War in 1899, following the discovery of gold in the Transvaal. A year prior, in 1898 patriotic American armies had defeated Spain in a series of battles to acquire sugar-rich Cuba and Puerto Rico, as well as the islands of Guam and Philippines. A war that ended the Spanish Empire effectively launched a new empire and American forces would soon be needed to protect expanding economic interests abroad.
In the hundred years following the defeat of Napoleon, numerous empires ruled by regal and noble families fought each other for colonies and the resources they provided. Competing for land, to forge their empires, were the armies of Russia, Germany, Austria-Hungary, France, Britain and the Ottomans, supported at home by a wildly nationalistic newspapers and magazines constantly feeding the appetites of naturally competitive humans, always hungry for more and prepared to fight, equally proud of their rulers' stance and each proclaimed victory in the field. 
The bubble burst in 1914. In the month that followed the assassination of Archduke Franz Ferdinand and his wife while traveling in a motorcade along a narrow Sarajevo street, battle lines were quickly drawn as were allies for the war to come. Nationalism fomented by imperialism, aided by militarism and fueled by capitalism, had launched the First World War. Indeed it was a global conflict fought on many lands, and many lives were lost, many millions in fact as empires collapsed. Recovery would take decades, and yet again the world was plunged into another war.
Queen Victoria had married Prince Albert, son of Ernst, Duke of Saxe-Coburg & Gotha in 1840, and remained a member of the House of Hanover. King Edward VII was the only British monarch of the House of Saxe-Coburg-Gotha, and he reigned for nine years at the beginning of the twentieth century, and was succeeded by King George V who replaced the German-sounding name with that of Windsor during The Great War. However, the title survived in other European monarchies, including the Belgian Royal Family and the former monarchies of Portugal and Bulgaria.
At the outbreak of war, the royal rulers of three empires were cousins: King George V of Britain, Tsar Nicholas II of Russia, and Kaiser Wilhelm II of Germany. In fact, all three were equal descendants of King George II of Britain. The struggle among them proved personal as George would deny Nicholas asylum after the Russian Revolution in 1917. After being captured by the Bolsheviks, Nicholas and his family would be subsequently executed by firing squad. 
Despite mobilizing its army against them - on behalf of Serbia - Russia did not declare war with either Germany or Austria-Hungary; whereas Germany declared war with Russia, France, Belgium and Portugal in August 1914 but not any other country, and Britain declared war with both Germany and Austria-Hungary, as well as Turkey and Bulgaria. It is estimated that 10 million military personnel died during the war (7 to 8 million due to combat and 2 to 3 million due to accidents, disease and while held captive), and there were nearly 7 million un-armed civilian deaths.