The United States facing defeat in Vietnam. Moscow defied in Czechoslovakia. Student uprisings in Berlin, Paris and Mexico. Fifty years ago the world was rocked by revolt and dashed hopes.

The longstanding relationship between the United States and Saudi Arabia, its main Middle East ally, is founded largely on the exchange of American security for Saudi oil.

Saudi Arabia's crown prince Mohammed bin Salman is set to meet with US President Donald Trump in Washington on Tuesday.

Mutual rival Iran will be high on the agenda, but the 32-year-old strongman prince will also be looking to showcase his sweeping changes to Saudi society and an increasingly assertive foreign policy that includes the war in Yemen and an ongoing diplomatic feud with Qatar.

Russia announced on Saturday the expulsion of 23 British diplomats in a tit-for-tat move following London's response to a nerve agent attack against a Russian former double agent in England.

The Syrian government launched a ferocious assault on a rebel enclave outside Damascus on February 18, saying it wanted to crush Islamist and jihadist groups.

As a teenager Kamal Jalal saw two of his sisters killed when Iraqi dictator Saddam Hussein's forces launched a gas attack on the Kurdish town of Halabja.

As Cuban President Raul Castro prepares to step down next month, ending his family's six-decade grip on power, his successor will be faced with major challenges, including the implementation of economic reforms vital for the island's future.

Syria enters its eighth year of war on Thursday, free of the jihadist "caliphate" but torn apart by an international power struggle as the regime presses its blistering reconquest.

The conflict that started on March 15, 2011 as the government of President Bashar al-Assad cracked down on mostly peaceful protests is raging on relentlessly and getting more complex.

Vladimir Putin is widely expected to win Russia's presidential election on Sunday, giving him a fourth term that would take him to nearly a quarter-century as the head of state or government.

A retired Russian double agent was leading a seemingly peaceful life in rural Britain when he and his visiting daughter were targeted in a nerve agent attack.