The year in review

Global developments

The Islamic State in Iraq and the Levant extended its bloody reach far beyond its base in Iraq and Syria. The group's barbarity was unrelenting. Gruesome propaganda included the burning alive in a cage of a Jordanian pilot whom ISIL had captured, the beheading of 21 Egyptian Coptic Christians in Libya and the murder of the 82-year-old head of antiquities at Palmyra, a heritage site in Syria that was looted by ISIL.

Western governments felt compelled to counter the threat, especially after ISIL claimed responsibility for an assault on Paris in which gunmen mowed down people in restaurants and bars and at a rock concert, killing 130 and injuring hundreds. President François Hollande declared that France was at war with ISIL.

After claiming that a Russian airliner had been bombed by ISIL affiliates in Egypt, Russia sent fighter jets to Syria, ostensibly to bomb ISIL. Most of its firepower, however, was directed at other opponents of the Syrian despot, Bashar Assad, a client of Vladimir Putin.

Turkey also entered the fray, after a student gathering was bombed in a town near the Syrian border. But Turkey also targeted the Kurdish PKK. Suicide-bombers in Ankara attacked a peace rally that called for an end to Turkey's actions against the Kurds, killing 102 people. The chaos only strengthened the hand of the ruling Justice and Development party, which won an election in November.

Around half the hundreds of thousands of people who streamed into Europe in the continent's worst refugee crisis since the Balkan wars came from Syria. The image of a 3-year-old Syrian boy found drowned on a Turkish beach caused widespread outrage. Several summits were held to try to resolve the crisis. Germany threw open its borders and is on course to accept more than 1 million asylum-seekers this year.

After years of talks, Iran and six world powers reached a deal on Iran's nuclear program. Some hailed it as a chance for Iran to come out of the cold. Others, notably Israel, said the deal was a mistake that would allow Iran to develop nuclear weapons and throw its weight around.

Global business

China's stock markets plunged during the summer, sending out global ripples. China's ham-handed attempts to stop the sell-off, such as directing large state investors to buy shares, did nothing to calm nerves. Nor did a sudden devaluation of the yuan. The whole episode raised questions about the state of China's slowing economy and the competence of its regulators.

The total value of announced takeovers in 2015 passed $4.3 trillion, breaking a record set in 2007. Pfizer's $160 billion purchase of Allergan, Dow Chemical's $130 billion merger with DuPont and Anheuser-Busch InBev's $110 billion acquisition of SAB Miller were three of the biggest in history. Other deals included Shell/BG Group ($70 billion), Charter Communications/Time Warner Cable ($55 billion), Anthem/Cigna ($52 billion) and Heinz/Kraft ($50 billion).

The tech industry passed several milestones. Dell's $67 billion takeover of EMC was the biggest to date. Facebook set a new record when a billion people logged onto the social network in a single day. But there were fears that the heady valuations of many private tech start-ups, also known as "unicorns," might turn out to be another bubble.

It was a dismal year for Volkswagen. A boardroom spat at the German carmaker led to the resignation of Ferdinand Piëch as chairman. VW was then embroiled in crisis in the autumn after admitting it had installed software on diesel cars that cheated emissions tests in the U.S.

A U.N. summit on climate change, held in Paris, produced an agreement that aims to hold the increase in the global average temperature to "well below 2°C above preindustrial levels," a more ambitious goal than had been expected. It marked an unprecedented political recognition of the risks of global warming, though some greens were skeptical that governments would follow through.

Politics and society

Britain's general election confounded the pollsters when the Conservative Party, which had governed in coalition with the Liberal Democrats for five years, secured its first overall majority in Parliament since 1992. The Lib Dems were reduced to a handful of MPs, whereas nationalists won all but three seats in Scotland. The opposition Labour Party went into self-destruct mode after the election by choosing Jeremy Corbyn, a leftist, as its new leader.

The polls also got it wrong in Canada, where the Conservative Party was chucked out of office and a new Liberal government, headed by Justin Trudeau, was voted in. In Israel Binyamin Netanyahu wrong-footed the pundits when he was returned to power as prime minister.

U.S. presidential candidates started their campaigns. Hillary Clinton wobbled under pressure about her use of an insecure private server for official e-mail, but remains the Democratic front-runner. The Republican establishment was unpleasantly surprised when Donald Trump soared into the lead in the party's race, despite badmouthing Mexicans and Muslims.

Gay marriage took two giant steps forward. It became legal throughout the U.S. when the Supreme Court ruled the constitution grants an "equal dignity" to gay couples. And Ireland became the first country to pass gay marriage by popular vote.

The U.S. suffered several mass shootings. In one, in Charleston, S.C., nine people at a black church were gunned down by a white supremacist. Elsewhere, the police were berated for excessive use of force. The worst riots in Baltimore since the 1960s were triggered by the death of a black man in police custody.