How to Change the World
There's no doubt that the assassination of Archduke Franz Ferdinand (pictured above, shortly before his death) was a turning-point in history. When Bosnian Serb nationalist Gavrilo Princip shot dead the heir to the Austro-Hungarian empire on June 28, 1914, he set in motion a chain of events that started World War I.

Nothing was quite the same after the Great War. The conflict cost an estimated eight million lives and was responsible for the break-up of four empires: Germany, Austria-Hungary, the Ottoman empire and Russia. Dozens of new states were created, spawning fresh tensions that are still playing out today. In addition, war itself altered irrevocably between 1914 and 1918. It was now yoked to industry in a way it had never been before. And it was being prosecuted on new fronts. Air war had arrived, bringing with it the prospect of bombing civilians. The concept of "total war" had been born.

Pity the Peacemaker
As Indians stood on the brink of independence from Britain in August 1947, one man above all others was responsible for getting them there. Mohandas "Mahatma" Gandhi's campaigns of non-violent protest were instrumental in persuading the British that it was time to relinquish the Raj. In late 1947, Gandhi was still serving his people, trying to heal bloody religious conflict caused by "Partition" - the hasty creation of Hindu India and Muslim Pakistan.

On January 30, 1948, Nathuram Godse, a Hindu extremist opposed to Gandhi's de facto support of Partition, shot the veteran peacemaker dead. After Gandhi's death, Indians and Pakistanis were forced to accept the bitter reality of Partition. If a man of peace like Gandhi had been consumed by religious hatred, what hope was there for ordinary citizens? More than half a century later, the two countries are still not fully reconciled.

Death of a Revolutionary
Ernesto "Che" Guevara was not a man to let the grass grow under his feet. When, in October 1965, after a decade of dedication to the Cuban revolution, he fell out with Fidel Castro, it didn't take him long to find another cause. By November 1966, Guevara had arrived in Bolivia to begin training anti-government guerrillas. But this was his last hurrah. On October 9, 1967, he was shot dead by CIA-backed Bolivian soldiers who had captured him a day earlier.

Guevara's death marked the end of the old-fashioned left-wing revolutionary. The Argentine-born radical had led armies in the field rather than sleeper cells committed to terrorism. In two decades, the Soviet Union - supporter of Cuba and countless other left-wing causes - would be on its knees. Guevara's death changed something else, too: bedroom walls of students all over the world are still decorated with posters of his iconic portrait.

Goodbye Mister President
Youthful war hero, charming intellectual, charismatic speaker - John F. Kennedy was everything you could hope for in a U.S. President. When he entered the White House in 1961, America was deeply embroiled in the Cold War and plagued by social and racial divisions. Nevertheless, during Kennedy's 1,037 days in office, there were signs of a brighter future.

Kennedy's presidency ended violently in Dallas on November 22, 1963, when he was assassinated by Lee Harvey Oswald. There was a huge outpouring of grief. The man who ought to have led the United States to a better place in the world and a better understanding of itself was gone. The nation knew something precious was lost forever but what was it? Maybe it was hope. Maybe it was youth. Whatever it was, Americans have never felt the same way about a president ever since.