The Arab Spring swept across the Middle East, toppling dictators in a rolling surge of street protest. Europe's currency plunged into crisis, bringing down elected prime ministers. An earthquake and tsunami pummeled Japan, confronting it with the specter of nuclear disaster.
It was a year that shook the pillars of the established order. Even in an era of change and moment-to-moment communications across the planet, 2011 felt extraordinary. Week after week, month after month, across continents and oceans, the news just kept on coming.
At times the post-World War II, post-colonial, post-Cold War dispensation seemed to tremble under shows of people power not seen in the 22 years since the fall of the Berlin Wall.
By year's end at least three Arab leaders were gone, and at least three European prime ministers had been toppled by the upheaval over the euro, a currency that was supposed to symbolize a strengthened, united Europe.
First to fall to the Arab Spring was President Zine El Abdine Ben Ali, cast into exile six weeks after a disgruntled vegetable vendor sparked an uprising by setting himself on fire.
The fastest revolution was Egypt's. It took just 18 days, and vast crowds gathered in central Cairo's Tahrir Square to force the resignation of President Hosni Mubarak. He had ruled the most populous Arab nation for nearly 30 years.
The bloodiest revolution was the one against Libya's Moammar Gadhafi, 42 years in power, who was toppled by a concerted NATO bombing campaign, then killed in circumstances still under investigation.
The slowest-burning revolt was Yemen's, stretching from February until November, when President Ali Abdullah Saleh agreed to step down by Friday. But he hadn't done so as of Saturday .
Still raging on were daily demonstrations against Syrian President Bashar Assad, in which the U.N. said more than 5,000 people died. The island kingdom of Bahrain fought street battles with its subjects; another kingdom, Jordan, experienced street protests.
The tensions didn't stop there. The U.N.'s atomic agency renewed accusations that Iran secretly worked on a nuclear weapon, Western sanctions on Iran intensified, and a mob seized the British Embassy in Tehran in retaliation.
The longer-term results of the convulsions triggered by the Arab Spring were far from clear.
The immediate outcome was a surge in support for long suppressed Islamic movements, whose strength was quickly apparent when Tunisia and Egypt held their first fully free elections in memory. The Islamist successes in Egypt threw into question Egypt's long-term alliance with the United States, its strongest financial and diplomatic backer, and its peace treaty with Israel, long supported by Mubarak but deeply unpopular in Egyptian public opinion.
Facebook and cellphone images played an important role in organizing protesters and getting dramatic scenes past the censors back home and onto the world's TV sets. They also were crucial to Israel's summer of discontent that brought multitudes onto the streets to protest high prices and inequalities; to Russians' unprecedented demonstrations against Prime Minister Vladimir Putin; and to the "occupy" movements that began in New York against Wall Street and spread to other continents in protest against those responsible for the financial meltdowns of the past two years.
Dysfunctional finances dominated the headlines in 2011, particularly in Europe, starting with a bailout for Greece's faltering economy. As other weak economies came under pressure and faced the likelihood of painful budget austerity, the prime ministers of Greece and Italy were forced to resign, and their Spanish counterpart was ousted in an election.
While street politics and financial fears dominated the headlines, the U.S.'s nearly nine-year war in Iraq reached its end with the low-key departure of the last American soldiers. It had left 4,500 Americans and 110,000 Iraqis dead, divided Americans, angered international public opinion and cost more than $800 billion. What was left was a fragile democracy and a potential for violence underscored by a bombing in December that killed 21 Shiite pilgrims in a religious procession.
Meanwhile, the war in Afghanistan ground on with more than 500 foreign troops, almost 400 of them American, killed in combat against the Taliban in 2011.
NATO had spent another year trying to train up to 350,000 Afghan troops and police to take over security once foreign forces are gone in 2014. But this year was marked by several spectacular Taliban operations, among them the downing of a U.S. military helicopter, killing 30 Americans and seven Afghan commandos aboard -- the war's single deadliest loss of American lives.
Osama bin Laden, mastermind of the 9/11 attacks on the United States, was killed by U.S. Navy SEALs who helicoptered into Pakistan and raided the house where he turned out to have been living.
The triumph was soured by recriminations with Pakistan, the United States' vital ally in the war against the Taliban, for invading its air space, and then by news that some of the SEALs who died on the downed helicopter in Afghanistan were from the same unit as those who killed bin Laden .
Meanwhile, just as Haiti's earthquake opened 2010 with the grimmest of news, March 2011 saw Japan's biggest earthquake on record send a tsunami crashing into the country's eastern coast, leaving 19,334 people dead or missing by government count, and inflicting damage estimated at nearly $220 billion.
At the Fukushima Dai-ichi nuclear power plant complex, three reactor cores melted down and radiation -- estimated at one-fifth of the amount released in the Chernobyl crisis -- poured into the surrounding air, water, soil and forests. Radiation leaks have since fallen dramatically, but a 12-mile zone round the plant remains off-limits and nearly 100,000 residents who fled their homes remain in limbo, unsure when they can return, if ever.
While nearly all the rubble along the coast has been cleared, rebuilding is only just beginning. But the overall economy has largely bounced back.
If the Japanese earthquake was Asia's worst horror of the year, Europe's took place in Norway, where a homegrown terrorist set off a bomb in Oslo's government district, then went to a summer camp dressed as a police officer and gunned down youths as they ran and swam for their lives. The attacks killed 77 people in the peaceful nation's worst violence since World War II. Psychiatric experts have since declared the self-styled anti-Muslim militant legally insane.
On the science front, the world said goodbye to the U.S. space shuttle as it closed three decades of service with its last flight in July. An E. coli bacteria outbreak in Europe spread to 15 countries and killed 68 people. Scientists reported sightings of particles that appeared to defy Albert Einstein's theories by traveling faster than light. Other scientists said they were closing in on a possible key building block to the universe popularly known as the "God particle."
Sex scandals took their turn in the headlines, first with charges that Italian Prime Minister Silvio Berlusconi paid an underage prostitute for sex, then with the arrest of Dominique Strauss-Kahn, head of the International Monetary Fund, accused of sexually assaulting a chambermaid in a Manhattan hotel. While Berlusconi faced trial, New York prosecutors dropped their case against Strauss-Kahn.
2011 witnessed a landmark in the political thawing of Myanmar, formerly Burma, long under military rule but making moves toward democracy that made possible a visit by Secretary of State Hillary Clinton.
Meanwhile, in Africa, a new nation was born out of civil war as South Sudan broke away from Sudan and became a U.N. member state. Palestine also set out to achieve membership but its bid stalled in the Security Council. However, the Palestinians managed this year to win recognition by UNESCO, the U.N. cultural agency.
In Central America, the Mexican drug war between cartels and government forces marked its fifth year, having claimed tens of thousands of lives. And Daniel Ortega, the one-time Sandinista revolutionary, was re-elected president of Nicaragua by a landslide, having sidestepped a constitutional limit on re-election.
For Britain, 2011 was a grim year of street riots and looting that shook its cities in the summer, and of revelations of privacy-invading foul play by its tabloid newspapers that appalled the nation. And as the year ended it found itself accused by its European partners of letting them down for refusing to join their pact to save the euro.
Yet all the same, the British managed to produce something to capture hearts around the world and offer assurance that some pillars of the old order still stand firm: the wedding of Kate Middleton to Prince William, son of the late Princess Diana -- a union of commoner and blueblood that promised to revitalize the British monarchy.