10. The Saudis Intervene in Yemen

Saudi Arabia launched air strikes in late March against its neighbor Yemen with the help of nine other, mainly Arab, countries. The move came after Houthi rebels captured Yemen’s capital Sanaa and drove Yemeni President Abdu Rabbu Mansour Hadi into exile in Saudi Arabia. The Houthis, who belong to a minority Shiite sect, receive support from Iran, Saudi Arabia’s mortal enemy. The Houthis also have the support of forces loyal to former Yemeni President Ali Abdullah Saleh, who was ousted during the Arab Spring and who once had good relations with Riyadh. The Saudi-led intervention put the United States in a bind. Washington feared that the intervention could become a quagmire and worried that al-Qaeda in the Arabian Peninsula (AQAP), an enemy to the Houthis as well as the United States, would benefit from the ensuing chaos. But the desire to prevent a rift with Riyadh prevailed, and Washington provided intelligence information, weapons, and aerial-refueling capabilities while urging the Saudi-led coalition to minimize civilian casualties. The civilian toll in Yemen has nonetheless been substantial, as air strikes and a maritime blockade have intensified Yemen’s many existing problems. As predicted, AQAP has used the fighting to its advantage, as has ISIS. In a potentially positive development, a seven-day ceasefire went into effect this month so that peace talks could begin.

9. China Builds Islands in the South China Sea

China claims much of the South China Sea—the bulk of which lies far from the Chinese mainland—through its so-called nine-dash line. Beijing is trying to give substance to its claims, which the five countries with coastlines on the sea vigorously dispute, by creating artificial islands around reefs and submerged rocks. It is in turn building airstrips and military installations on the newly formed islands. The United States takes no position on the merits of China’s claims in the South China Sea. But the U.S. insists China’s claim that the 12-mile zone around these new islands constitutes its territorial waters has no basis in international law. Washington—and most governments in Southeast Asia—worry that Beijing will eventually use the new islands to choke off freedom of navigation in the area. In October, after repeated official statements about how “the United States will fly, sail, and operate wherever international law allows,” a U.S. Navy destroyer sailed through waters China claims as its own in a freedom-of-naval-operations (FONOPS) mission. China protested the maneuver as “a very serious provocation politically and militarily.” The stakes in the dispute are enormous. More than $5 trillion in trade passes through the South China Sea each year, and its waters contain rich fisheries and potentially vast oil and mineral deposits. And then there is the question of whether China will supplant the United States as the dominant power in the region.

8. China Devalues the Renminbi Amid an Economic Slowdown

Beijing sent shock waves through global financial markets in August when it devalued its currency, variously called the yuan or renminbi, against the dollar. Chinese officials said the move was intended to bring the yuan in line with its market value, something Western governments had been urging for years. Many investors took the devaluation as a sign that the Chinese economy was slowing down faster than reported and that Beijing was using its currency to try to reignite growth. The Shanghai stock market plunged in late August, further unsettling global markets and shaking confidence in China’s handling of economic policy. In October, China reported that third-quarter growth hit 6.9 percent, which was higher than expected but well below the 10-percent growth China has averaged over the past three decades. And doubts exist about the accuracy of the numbers that Beijing reported. Despite the bad economic news coming out of China, the International Monetary Fund in December designated the renminbi as a major world currency, which opens the door to its greater use in global financial transactions. But investors and governments remain nervous that China’s economy, which has been a major driver of global growth in recent years, will continue to slow, and as a result, so will economic growth around the world.

7. The World Strikes a Deal on Climate Change

The world’s climate is changing, in good part because of human activity. But governments around the world have been slow to address the potentially catastrophic threat. The landmark 1992 Kyoto Treaty failed to deliver its promised emissions cuts, and not just because the U.S. Senate declined to provide its consent. The 2009 Copenhagen climate summit opened to much fanfare but was laced with acrimony and produced little. The 195 countries that turned up in Paris in late November for a new climate-change summit avoided that fate. After two weeks of intense talks, they produced the Paris Climate Accord, the first to commit nearly every country to reduce its emissions of heat-trapping gases. The 31-page document hardly solves the climate-change challenge, however, which is why some climate-change activists criticized it for being too little, too late. To get the deal, negotiators left a lot of the details to be worked out later. Even if agreement is reached on those details, the success of the Paris Climate Accord ultimately depends on national governments taking, and enforcing, steps to reduce reliance on fossil fuels. Domestic politics could be a major hurdle on that front.

6. Russia Intervenes in Syria

The four-year-long Syrian Civil War, which has killed more than 200,000 people and forced as many as 9 million to flee their homes, took a turn in September when Russia without warning began conducting air strikes from bases in Syria. Moscow insisted it intervened to join the fight against the self-proclaimed Islamic State, but in practice its planes targeted Syrian rebel groups looking to topple Russia’s longtime ally, Syrian President Bashar al-Assad. Russia’s military operations were not coordinated with those the United States and its allies were conducting against the Islamic State, raising concerns about an unintended confrontation between the two sides. A version of those fears materialized in late November when Turkish F-16s shot down a Russian fighter jet, killing one of the pilots. Turkish officials insisted that the Russian plane had ignored repeated warnings not to enter Turkish airspace. Russian officials disputed those claims and accused Ankara of a “planned provocation.” On the diplomatic side, Russia’s intervention prompted an effort to find a negotiated settlement to the Syrian conflict. Despite significant fanfare and high-level participation on all sides, the talks stumbled over a core disagreement: Moscow wants Assad to stay, Washington and its allies want him to go.

5. The Trans-Pacific Partnership Finally Gets Done

After seven years of negotiations, the United States and 11 other countries finally reached agreement in October on the Trans-Pacific Partnership (TPP), the largest regional trade deal in history. The agreement, which is a critical part of the Obama administration’s rebalance to Asia, would set trade rules governing roughly 40 percent of the global economy. The deal was made possible when the U.S. Congress voted in June to give President Barack Obama Trade Promotion Authority (TPA), which among other things restricts Congress to a simple up-down vote on trade deals. U.S. negotiating partners had refused to make major concessions in the TPP negotiations until they knew that Congress could not revise the deal that they negotiated with the president. In a sign of how controversial trade deals can be on Capitol Hill, just 41 Democrats voted for TPA. Now that Obama has TPP, he has to persuade Congress to pass the bill to put it into effect. Critics are already marshaling their arguments for why Congress should vote down the implementing legislation. A vote on TPP likely won’t happen until after the 2016 elections, if it happens at all.

4. The EU Rebuffs Greece’s Demand for Austerity Relief

I fought the law and the law won.” Alexis Tsipras learned the hard way what the Bobby Fuller Four only sang about. Tsipras became the Greek prime minister in January 2015 by pledging to get Greece better repayment terms on its massive debt. Despite appealing to other debt-burdened European countries for solidarity and trying to isolate EU power Germany by dredging up memories of Nazi atrocities, the European Union refused to give Tsipras what he wanted. He then tried to strengthen his hand by calling a July referendum in which 61 percent of Greeks voted against accepting the EU’s offer. The EU nonetheless held firm, insisting that Greece would get help only if it agreed to significant, and painful, economic reforms. Tsipras blinked. A week after the ‘no’ vote, and faced with the imminent collapse of the Greek economy, he accepted the EU’s offer. Despite not delivering the relief that he promised, Tsipras and his Syriza Party won new elections in September. But Greece’s economy remains troubled. It has shrunk by 25 percent over the past five years, official unemployment is nearly 25 percent, and doubts remain over whether Greece can ever repay its debts as long as it remains in the euro zone. So “Grexit,” and its possible shock to the global financial system, could soon be back in the news.

3. Negotiations on Iran’s Nuclear Program Produce a Deal

If at first you don’t succeed, try, try again. That old saying could be the motto of the Iran nuclear negotiations. Conducted off and on since 2002, they finally produced a deal in July. Formally called the Joint Comprehensive Plan of Action (JCPOA), it wasn’t sealed until September, when 42 Democratic senators voted to block a resolution to stop it. Neither the P5+1 nor Iran got all it wanted in the JCPOA. Iran got sanctions relief, but it had to agree to give up 97 percent of its stockpile of enriched uranium, slash its number of centrifuges by two-thirds, and shut down a heavy-water reactor. Iran also had to agree to on-site inspections by the International Atomic Energy Agency. If Iran violates the JCPOA, sanctions can be reimposed. To extract these concessions from Iran, the P5+1 agreed to let the deal’s critical provisions expire after 10 or 15 years. The White House says the deal will prevent Iran from acquiring a nuclear weapon for more than a decade and increase the “breakout time” should Tehran decide to acquire nuclear weapons. The deal’s critics—and there are many, both at home and abroad—say the deal failed to deliver the only acceptable outcome: dismantlement of Iran’s nuclear program.

2. ISIS Terrorists Strike on Three Continents

When Obama told an interviewer on November 12 that “we have contained” the Islamic State, he had in mind its geographical ambitions in the Middle East. A day later, the world discovered that the Islamic State was taking its fight beyond its home territory. Three teams of ISIS terrorists struck at four locations in Paris, killing 130 people. But ISIS’s efforts to take the fight to its enemies had begun even earlier. In July, a suicide bomber loyal to the Islamic State killed 33 people in Suruc, Turkey, not far from the border with Syria. Three months later, two suicide bombers, one the brother of the Suruc bomber, killed 102 people at a peace rally in Ankara. On October 31, a bomb brought down a Russian passenger airliner over the Sinai, killing all 224 people on board. And then on December 2, a husband and wife who had pledged allegiance to the Islamic State’s caliph, Abu Bakr Al-Baghdadi, killed 14 people in a mass shooting in San Bernardino, California. The attacks prompted renewed Western air strikes against the Islamic State, redirected domestic politics in France and the United States, and raised ominous questions about what 2016 might bring.

1. A Refugee Crisis Roils Europe

A decade ago, experts were writing books with titles like Why Europe Will Run the 21st Century. In 2015, Europe hardly looked capable of handling its own problems, let alone running the world. Still struggling to emerge from a deep economic recession, it was hit by a wave of nearly a million refugees. Most were seeking to escape the horrors of the Syrian Civil War or instability and violence elsewhere. Others, however, were economic migrants seeking better job opportunities. The influx of refugees provided heart-wrenching images of people desperate to reach Europe,sometimes failing with deadly consequences, but more often succeeding. The influx exposed Europe’s porous borders, highlighted differences within Europe over how to handle immigrants, and gave new life to Europe’s many nationalist and anti-immigrant parties. The refugee crisis also created political problems across the Atlantic. The Obama administration announced in September that it would take in “at least 10,000” Syrian refugees in 2016. But in the aftermath of the Paris and San Bernardino attacks, compassion quickly swung to concern, and federal, state, and local politicians moved to block Muslim refugees from entering the United States or relocating to their communities. As long as Syria’s civil war persists and the European economy attracts job-seekers, the refugee and migrant pressure on Europe will continue.

Other stories of note in 2015 included Obama’s decision to reverse course and keep U.S. combat troops in Afghanistan through the end of his presidency, ongoing peace negotiations in Colombia, escalating tensions in the West Bank and Jerusalem, the discovery of debris from Malaysia Airlines Flight 370 on Reunion Island, a collapsed crane in Mecca and a deadly stampede at the Hajj, China’s decisions to abandon a one-child policy in favor of a two-child policy, and the arrests (yes, there were more than one) of senior officials at FIFA, the organization that oversees soccer (or “football”) around the world.

This post appears courtesy of the Council on Foreign Relations.