Washington (CNN) On Thursday, President Barack Obama declared in an interview that ISIS had been "contained," asserting that the terror cell had been stalled in Iraq and Syria.

The next day, ISIS claimed responsibility for one of the worst terror attacks in European history, shattering what had been a growing sense of momentum in the global fight against extremists and driving home the frightening ability of ISIS to inspire and possibly coordinate attacks outside their power base in Iraq and in Syria.

"We, including the President, have said from beginning the fight against ISIL would be long and have both good and bad days," according to a senior administration official pressed to explain the apparent disconnect between Obama's comments and the spectacular set of coordinated attacks that stunned Europe and killed more than 120 people out on a Paris Friday night.

President Obama said ISIS was "contained" before Paris attack

President Obama said ISIS was "contained" before Paris attack 01:08

President Obama said ISIS was "contained" before Paris attack

It is not yet clear who exactly perpetrated the Paris attacks, but the French government has blamed ISIS and U.S. officials have said there is no reason to doubt that assertion.

The stated goal of the U.S. had been to decapitate ISIS, but the group, claiming credit for the attacks in Paris, has shown that containment and decapitation clearly don't work against an organization that courts death and is atomized to the point individuals or small groups can act largely on their own. ISIS has quickly matured during the Obama administration from a group the President once called al Qaeda's "JV team" to a terrifying threat to the West. It's a threat the U.S. and Europe clearly do not yet fully understand.

Before the attack, Obama spoke reassuringly about the growth of ISIS in the MIddle East, suggesting that while the terror group had not been beaten, it had been controlled.

"We have not yet been able to ... completely decapitate their command and control structures," he told ABC News. But he touted success in "trying to reduce the flow of foreign fighters."

The administration says when he declared ISIS contained, Obama was speaking only about efforts to help Iraqi and Kurdish forces and U.S. bombing efforts in Syria.

Recent wins against the group seemed to back up Obama's assertion: Kurdish forces retook Sinjar Mountain in Iraq with the help of U.S. airpower late this week. A drone strike announced late Thursday is suspected to have killed "Jihadi John," the ISIS executioner, a symbolic victory after Americans and others were killed on camera and used in propaganda videos. And overall, ISIS' capture of ground has slowed.

"It means exactly what he said," the senior administration official said, referring to the President's containment comments. "Their (ISIS) momentum in terms of territorial gains in Iraq and Syria has been contained/halted."

Photos: Landmarks turn blue, white and red in support for Paris Photos: Landmarks turn blue, white and red in support for Paris The Eiffel Tower in Paris is illuminated in the French national colors on Monday, November 16. Displays of support for the French people were evident at landmarks around the globe after the deadly terrorist attacks in Paris on Friday, November 13. Hide Caption 1 of 27 Photos: Landmarks turn blue, white and red in support for Paris The world's tallest tower, Burj Khalifa, is lit in French colors Sunday, November 15 in Dubai, United Arab Emirates. Hide Caption 2 of 27 Photos: Landmarks turn blue, white and red in support for Paris A man walks past Jerusalem's Old City walls, which were illuminated in the colors of the French flag on November 15. Hide Caption 3 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Tokyo Skytree is lit up in the colors of the French flag on November 15. Hide Caption 4 of 27 Photos: Landmarks turn blue, white and red in support for Paris A paddlewheel riverboat passes under a bridge in Nashville, Tennessee, on Saturday, November 14. Hide Caption 5 of 27 Photos: Landmarks turn blue, white and red in support for Paris Estonia's government building in Tallinn glows with the French national colors on November 14. Hide Caption 6 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Peace Bridge, which connects Canada and the United States, glows with the colors of the French flag November 14 in Buffalo, New York. Hide Caption 7 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Staples Center's ice is lit up with the colors of the French flag before the start of an NHL hockey game on November 14. Hide Caption 8 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Christ the Redeemer statue in Rio de Janeiro is illuminated in French national colors on November 14. Hide Caption 9 of 27 Photos: Landmarks turn blue, white and red in support for Paris As the sun sets, London's Tower Bridge is lit in a succession of blue, white and red on November 14. Hide Caption 10 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Palace Albania building in Belgrade, Serbia, is lit in the colors of the French flag on November 14. Hide Caption 11 of 27 Photos: Landmarks turn blue, white and red in support for Paris The White Tower, a symbol of the Greek city of Thessaloniki, is lit with the colors of the French national flag on November 14. Hide Caption 12 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Southbank Centre in London lights the cloudy sky on November 14. Hide Caption 13 of 27 Photos: Landmarks turn blue, white and red in support for Paris People in Tel Aviv, Israel, light candles and hold posters during a gathering to honor the victims of the Paris attacks on November 14. Hide Caption 14 of 27 Photos: Landmarks turn blue, white and red in support for Paris The London Eye reflects onto the River Thames on November 14. Hide Caption 15 of 27 Photos: Landmarks turn blue, white and red in support for Paris People cross the street past the Cibeles Palace, Madrid's town hall, on November 14. Hide Caption 16 of 27 Photos: Landmarks turn blue, white and red in support for Paris London's National Gallery is illuminated in blue, white and red lights on November 14. Hide Caption 17 of 27 Photos: Landmarks turn blue, white and red in support for Paris Friends Arena in Solna, Sweden, is illuminated in blue, white and red on November 14. Hide Caption 18 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Brandenburg Gate in Berlin stands illuminated in the colors of the French flag as people lay candles and flowers at the adjacent French Embassy on November 14. Hide Caption 19 of 27 Photos: Landmarks turn blue, white and red in support for Paris A ferry travels past the Oriental Pearl Tower in Shanghai, China, on November 14. Hide Caption 20 of 27 Photos: Landmarks turn blue, white and red in support for Paris As a sign of solidarity , Australia's Sydney Opera House is illuminated in the colors of the French flag on November 14. Hide Caption 21 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Calgary Tower in Alberta, Canada, is lit up with the colors of the French flag on Friday, November 13. Hide Caption 22 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Senate building in Mexico City is lit up blue, white and red on November 13. Hide Caption 23 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Auckland Museum in New Zealand is illuminated in French colors on November 13. Hide Caption 24 of 27 Photos: Landmarks turn blue, white and red in support for Paris In New York, the antenna of One World Trade Center was lit on November 13.

Hide Caption 25 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Eiffel Tower replica at Paris Las Vegas was dimmed over the weekend. Hide Caption 26 of 27 Photos: Landmarks turn blue, white and red in support for Paris The Taipei 101 building in Taiwan is illuminated blue, white and red. Have you seen other world landmarks lit up in tribute to France? Share your photos with CNN by tagging #CNNiReport on social networks. Hide Caption 27 of 27

Even before Obama's "contained" comment regarding ISIS in Iraq and Syria, the group's influence beyond those countries' borders was on full display as ISIS claimed responsibility for attacks in Beirut and the downing of a Russian passenger plane in Sinai.

The Paris attack further throws U.S. and Western counterterror efforts on their head. A White House official told CNN that before departing for a trip to Turkey and Asia and a G20 Summit, the President will "convene his National Security Council to review the latest intelligence surrounding the attacks in Paris."

U.S. officials have deferred to the French investigation.

"At this early stage, we have seen nothing that contradicts President Hollande's assessment of the situation," according to a senior U.S. intelligence official, referring to the French casting blame on ISIS.

"This is a French counterterrorism investigation and we are working with French officials to provide any assistance they may need," according to the official. "When they are able to share information and we, in turn, are able to share public details, we will do so."

But the event is sure to cause reassessments of strategies in the U.S. and Europe, both inside their countries and for how to deal with ISIS in the Middle East.

Photos: Increased security following Paris attacks Photos: Increased security following Paris attacks People go through a security checkpoint to attend a Mass in homage to victims of the Paris terror attacks at Notre Dame cathedral in Paris on Sunday, November 15. French President Francois Hollande declared a state of emergency after the attacks in Paris on Friday, November 13, and said border security has been ramped up. The terrorist group ISIS claimed responsibility for the attacks. Hide Caption 1 of 13 Photos: Increased security following Paris attacks French Prime Minister Manuel Valls, center, speaks with police forces with French Interior minister Bernard Cazeneuve, left, and Defence Minister Jean-Yves Le Drian at the Gare du Nord railway station in Paris on November 15 about security measures after the attacks. Hide Caption 2 of 13 Photos: Increased security following Paris attacks French police secure the perimeter after panic broke out among mourners who paid their respects at the attack sites at restaurant Le Petit Cambodge and the Carillon Hotel in Paris on November 15. Hide Caption 3 of 13 Photos: Increased security following Paris attacks Mounted police officers patrol in front of the Eiffel Tower in Paris on November 15. Hide Caption 4 of 13 Photos: Increased security following Paris attacks Security personnel inspect vehicles at the border between Belgium and France on Saturday, November 14. Hide Caption 5 of 13 Photos: Increased security following Paris attacks A police officer stands guard outside the Cafe Bonne Biere in the Rue de la Fontaine au Roi in Paris on November 14. Hide Caption 6 of 13 Photos: Increased security following Paris attacks A French police officer guards the French-Italian border on November 14 in Menton, France. Hide Caption 7 of 13 Photos: Increased security following Paris attacks Soldiers from the 3rd Marine Infantry Parachute Regiment of Carcassonne arrive at Charles de Gaulle Airport in Paris as security reinforcements on November 14. Hide Caption 8 of 13 Photos: Increased security following Paris attacks Soldiers patrol the Eiffel Tower on November 14. Hide Caption 9 of 13 Photos: Increased security following Paris attacks French police check vehicles on the bridge between Strasbourg and Kehl, Germany, on November 14. Hide Caption 10 of 13 Photos: Increased security following Paris attacks Police vehicles are parked near the entrance to the Louvre in Paris on November 14. Interior Minister Bernard Cazeneuve said the state of emergency in France could mean restrictions on people's movements. Airports in France remained open, and airlines were still flying there, though some airlines reported canceled flights. Hide Caption 11 of 13 Photos: Increased security following Paris attacks French police check vehicles on the so-called European bridge between Strasbourg and Kehl, Germany, on November 14. Hide Caption 12 of 13 Photos: Increased security following Paris attacks Police stand guard at a train station in Paris on November 14. Hide Caption 13 of 13

Control by ISIS of territory in Iraq and Syria versus the ability to project attacks outside of its base are, of course, separate issues. U.S. counterterrorism officials worried the latter would be the second phase the ISIS fight.

While ISIS was gaining and solidifying control of territory, external attacks weren't its priority. But the concern among counterterror officials was that once the U.S. and others began attacking to curb the territorial expansion, or even causing some retreat, ISIS would start sending back its legions of westerners or try to infiltrate fighters to conduct attacks. U.S. counterterrorism officials expected that Europe, particularly countries with big foreign-fighter numbers, would be first to feel this.

World leaders to convene

The battle against ISIS was already slated to occupy large portions of the agenda of the large meeting of global leaders in Turkey that Obama is set to attend. White House officials, speaking before the Paris attack, said Obama was eager to shore up the global coalition of nations that have joined to battle the group.

Now those discussions will assume an even greater urgency. Obama was originally planning to speak with French President Francois Hollande at the G20 gathering, but Hollande said Friday he was canceling his trip to Turkey.

That leaves other key players, including Obama, German Chancellor Angela Merkel and British Prime Minister David Cameron, to develop a response plan at the summit, being held at a resort on the Turkish Riviera. Leaders were already scheduled to meet for a working dinner focused on combating ISIS on Sunday, and Obama will meet with the leaders five major European allies Monday afternoon.

Obama will also encounter Russian President Vladimir Putin, whose recent efforts in Syria forced the administration to retool its strategy. While no formal meeting between the two men is planned, Obama's aides said there's ample opportunity for a talk.

Earlier efforts to combat extremism

The January attack by Islamic extremists against the French humor magazine Charlie Hebdo prompted a reckoning in Europe about the flow of foreign fighters onto the continent, and the pervasive appeal of Islamic extremism on disillusioned youth. At least one of the Charlie Hebdo attackers pledged allegiance to ISIS online, though none were known to be operating under direct orders from the group's leadership.

Photos: World reacts to Paris attacks Photos: World reacts to Paris attacks President Barack Obama, French President Francois Hollande, second from right, and Paris Mayor Anne Hidalgo arrive at the Bataclan, site of one of the Paris terrorists attacks, to pay their respects to the victims after Obama arrived in town for the COP21 climate change conference early on Monday, November 30, in Paris. Hide Caption 1 of 40 Photos: World reacts to Paris attacks The Eiffel Tower in Paris is illuminated in the French national colors on Monday, November 16. Displays of support for the French people were evident at landmarks around the globe after the deadly terrorist attacks in Paris on Friday, November 13. Hide Caption 2 of 40 Photos: World reacts to Paris attacks People hold hands as they observe a minute of silence in Lyon, France, on November 16, three days after the Paris attacks. A minute of silence was observed throughout the country in memory of the victims of the country's deadliest violence since World War II. Hide Caption 3 of 40 Photos: World reacts to Paris attacks French President Francois Hollande, center, flanked by French Prime Minister Manuel Valls, right, and French Education Minister Najat Vallaud-Belkacem, center left, stands among students during a minute of silence in the courtyard of the Sorbonne University in Paris on November 16. Hide Caption 4 of 40 Photos: World reacts to Paris attacks A large crowd gathers to lay flowers and candles in front of the Carillon restaurant in Paris on Sunday, November 15. Hide Caption 5 of 40 Photos: World reacts to Paris attacks A man sits next to candles lit as homage to the victims of the deadly attacks in Paris at a square in Rio de Janeiro on November 15. Hide Caption 6 of 40 Photos: World reacts to Paris attacks People light candles in tribute to the Paris victims on November 15 in Budapest, Hungary. Hide Caption 7 of 40 Photos: World reacts to Paris attacks People gather outside Notre Dame Cathedral in Paris on November 15 for a national service for the victims of the city's terror attacks. Hide Caption 8 of 40 Photos: World reacts to Paris attacks People write messages on the ground at Place de la Republique in Paris on November 15. Hide Caption 9 of 40 Photos: World reacts to Paris attacks People pray during a candlelight vigil for victims of the Paris attacks at a church in Islamabad, Pakistan, on November 15. Hide Caption 10 of 40 Photos: World reacts to Paris attacks French golfer Gregory Bourdy passes a peace symbol for the Paris victims during the BMW Shanghai Masters tournament November 15 in Shanghai, China. Hide Caption 11 of 40 Photos: World reacts to Paris attacks A man offers a prayer in memory of victims of the Paris attacks at the French Embassy in Tokyo on November 15. Hide Caption 12 of 40 Photos: World reacts to Paris attacks A woman holds a candle atop a miniature replica of the Eiffel Tower during a candlelight vigil Saturday, November 14, in Vancouver, British Columbia. Hide Caption 13 of 40 Photos: World reacts to Paris attacks Front pages of Japanese newspapers in Tokyo show coverage and photos of the Paris attacks on November 14. Hide Caption 14 of 40 Photos: World reacts to Paris attacks An electronic billboard on a canal in Milan, Italy reads, in French, "I'm Paris," on November 14. Hide Caption 15 of 40 Photos: World reacts to Paris attacks The Eiffel Tower stands dark as a mourning gesture on November 14, in Paris. More than 125 people were killed in a series of coordinated attacks in Paris on Friday. People around the world reacted in horror to the deadly terrorist assaults. Hide Caption 16 of 40 Photos: World reacts to Paris attacks Lithuanians hold a candlelight vigil in front of the French Embassy in Vilnius, Lithuania, on November 14. Hide Caption 17 of 40 Photos: World reacts to Paris attacks Thousands gather in London's Trafalgar Square for a candlelit vigil on November 14 to honor the victims of the Paris attacks. Hide Caption 18 of 40 Photos: World reacts to Paris attacks A woman lights candles at a memorial near the Bataclan theater in Paris on November 14. Hide Caption 19 of 40 Photos: World reacts to Paris attacks A man places a candle in front of Le Carillon cafe in Paris on November 14. Hide Caption 20 of 40 Photos: World reacts to Paris attacks A woman holds a French flag during a gathering in Stockholm, Sweden, on November 14. Hide Caption 21 of 40 Photos: World reacts to Paris attacks Nancy Acevedo prays for France during the opening prayer for the Sunshine Summit being held at Rosen Shingle Creek in Orlando, Florida on November 14. Hide Caption 22 of 40 Photos: World reacts to Paris attacks French soldiers of the United Nations' interim forces in Lebanon observe the national flag at half-staff at the contingent headquarters in the village of Deir Kifa on November 14. Hide Caption 23 of 40 Photos: World reacts to Paris attacks A couple surveys the signature sails of the Sydney Opera House lit in the colors of the French flag in Sydney on November 14. Hide Caption 24 of 40 Photos: World reacts to Paris attacks A woman places flowers in front of the French Consulate in St. Petersburg, Russia, on November 14. Hide Caption 25 of 40 Photos: World reacts to Paris attacks Candles are lit in Hong Kong on November 14 to remember the scores who died in France. Hide Caption 26 of 40 Photos: World reacts to Paris attacks A woman lights a candle outside the French Consulate in Barcelona, Spain, on November 14. Hide Caption 27 of 40 Photos: World reacts to Paris attacks Britain's Prince Charles expresses solidarity with France at a birthday barbecue in his honor near Perth, Australia, on November 14. Hide Caption 28 of 40 Photos: World reacts to Paris attacks The French national flag flutters at half-staff on November 14 at its embassy in Beijing. Hide Caption 29 of 40 Photos: World reacts to Paris attacks Dutch Prime Minister Mark Rutte after a speech on November 14 in The Hague following the attacks. Hide Caption 30 of 40 Photos: World reacts to Paris attacks Japanese Prime Minister Shinzo Abe becomes emotional after his speech on the French attacks during the opening ceremony of a Japanese garden in Istanbul, Turkey, on November 14. Hide Caption 31 of 40 Photos: World reacts to Paris attacks A woman mourns outside Le Carillon bar in the 10th district of Paris on November 14. The attackers ruthlessly sought out soft targets where people were getting their weekends underway. Hide Caption 32 of 40 Photos: World reacts to Paris attacks People lay flowers outside the French Embassy in Moscow on November 14. Hide Caption 33 of 40 Photos: World reacts to Paris attacks Mourners gather outside Le Carillon bar in the 10th district of Paris on November 14. "We were listening to music when we heard what we thought were the sounds of firecrackers," a doctor from a nearby hospital who was drinking in the bar with colleagues told Le Monde. "A few moments later, it was a scene straight out of a war. Blood everywhere." Hide Caption 34 of 40 Photos: World reacts to Paris attacks People attend a vigil outside the French Consulate in Montreal. Prime Minister Justin Trudeau offered "all of Canada's support" to France on Friday, November 13, in the wake of the attacks. Hide Caption 35 of 40 Photos: World reacts to Paris attacks Police show a heightened presence in Times Square in New York on November 13, following the terrorist attacks in Paris. Hide Caption 36 of 40 Photos: World reacts to Paris attacks People light candles at a vigil outside the French Consulate in Montreal on November 13. Hide Caption 37 of 40 Photos: World reacts to Paris attacks University of Nevada, Las Vegas, fans observe a moment of silence for the victims of the terrorist attacks in Paris before a basketball game November 13. Hide Caption 38 of 40 Photos: World reacts to Paris attacks The house lights are shut off and scoreboard dark as Boston Celtics players pause for a moment of silence for the Paris victims before an NBA basketball game against the Atlanta Hawks in Boston on November 13. Hide Caption 39 of 40 Photos: World reacts to Paris attacks People light candles at a vigil outside the French Consulate in Montreal on November 13. Hide Caption 40 of 40

In the aftermath of the attacks, Obama convened a summit in Washington aimed at countering violent extremism. The gathering was long-delayed from the fall, and finally placed on the schedule as a response to the Paris violence.

Officials said at the time he wanted to collect knowledge on how best to identify and counter violent extremists in the U.S. and abroad -- but refused to identify Islamic extremism as the primary focus of the gathering.

"I don't quibble with labels. I think we all recognize that this is a particular problem that has roots in Muslim communities," Obama told CNN's Fareed Zakaria in a January interview. "But I think we do ourselves a disservice in this fight if we are not taking into account the fact that the overwhelming majority of Muslims reject this ideology."

Earlier in the year, Obama chaired a session of the United Nations Security Council meant to address the flow of foreign fighters coming from Syria, following up on the meeting during this year's general assembly by saying he wanted to focus on the origins of extremism.

But even with those efforts in place, Obama's aides admit there's no quick solution to the pervasive problems facing Europe and the United States.

"It is not about a single meeting or a single event," Obama's National Security Adviser Susan Rice said ahead of the President's trip to the G20. "These issues are hugely complex and fraught. If they weren't, they would have been resolved a long time ago."