Paris held a "unity rally" on Sunday which was attended by world leaders from more than 40 nations, including German Chancellor Angela Merkel, UK Prime Minister David Cameron, Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas.
The event is believed to have been the biggest rally in French history and follows last week's multiple terrorist atrocities, which killed some 17 citizens, the worst such attacks in Europe since London in 2005.
One of the disturbing discoveries from the atrocities is the apparent link between at least one of the Paris terrorists, Said Kouachi, and al-Qaeda in the Arabian Peninsula (AQAP). It is reported that Kouachi met with the radical cleric Anwar-al Awlaki in Yemen in 2011, and may have received a period of terrorist training there and/or fought alongside AQAP.
Moreover, a pre-recorded video emerged on Sunday featuring another of the terrorists, Amedy Coulibaly, in which he pledged allegiance to the so-called Islamic State (IS). French officials are still searching for Coulibaly's wife, Hayat Boumeddiene, a potential accomplice to the attacks, who it is reported may have fled to Syria.
There remain unanswered questions about whether the Paris terrorists were merely potentially inspired by AQAP and/or IS, or if either group played a role in directing and/or providing operational support for the attack. Western intelligence officials are now urgently piecing together the facts.
However, what it is already clear is that the atrocities will fuel concerns of world leaders about foreign jihadists returning to their home countries from the Middle East. US President Barack Obama last year expressed his "deep concern" about this issue, echoing comments of others, including Australian Prime Minister Tony Abbott and Mr Cameron.
FBI Director James Comey has even warned about the prospect of a "future 9/11" caused by the increased flow of foreign fighters from the Middle East. In his view, "all of us with a memory of the 1980s and 1990s saw the line drawn from Afghanistan ... to Sept 11. We see Syria as that, but an order of magnitude worse" because of the larger number of foreign jihadists in the country.
The numbers of foreign fighters who have already returned from the Middle East to their home countries is not certain. However, Richard Barrett, the former Head of Counter-terrorism at the UK's MI6, warned last year that "up to 300" foreign fighters from Syria may now be back in Britain alone.
The International Centre for the Study of Radicalisation at King's College London estimates that as many as 11,000 foreign fighters overall may have fought in Syria, from some 74 countries, the majority from Arab countries.
A central concern is that a significant number of these individuals, who include potentially as many as 2,000 from Western Europe (possibly as many as 400 from France), plus others from North America, Australia, Southeast Asia, and Africa, will return battle hardened with significantly greater terrorist capability and resolve.
The Paris attacks provide a propaganda coup for al-Qaeda at a time when its fortunes had appeared to be ebbing. The group has endured ongoing disagreement with IS which was created in April 2013 from one of al-Qaeda's affiliation organisations in Iraq. Both sides have since disavowed each other with IS accusing al-Qaeda last year of having "deviated from the correct path" and "divided the mujahedeen in every place".
Moreover, some three and a half years on from Osama bin Laden's assassination, al-Qaeda's central organisation has been significantly depleted. Ayman al-Zawahri lacks bin Laden's personal authority within the network, and the core has also been weakened by the assassination of numerous other senior terrorist leaders.
A fundamental challenge for Mr Zawahri is that the central al-Qaeda leadership appears to still remain located largely in Pakistani tribal areas and borderlands. However, the wider network has becoming increasingly decentralised and dispersed and thus less able to control.
Accompanying this dispersion and decentralisation has been shifting focus of al-Qaeda groups and franchises whose attention in recent years has generally been as much on "local" national or regional issues, rather than the grander international designs of bin Laden. In part, this probably reflects the greater difficulty of attacking key international targets many of whose defences have become significantly hardened since 9/11.
There has also been evolution in the geographical focal points of al-Qaeda activity. Terrorist nodes of growing importance, for instance, have grown in key African and Middle Eastern countries, including Yemen, where political upheaval since bin Laden's death has allowed terrorists and other insurgents to secure greater foothold.
AQAP was formed in 2009 as a "merger" between al-Qaeda's Yemeni and Saudi branches. The organisation is believed by US officials to have undertaken a series of bomb plots against US targets, including the foiled plan to bring down a Detroit-bound plane in 2009 using explosives hidden in a terrorist's underwear.
Reflecting the changed geographical risk pattern from al-Qaeda, US forces have redeployed themselves. For instance, the CIA has expanded its staff in Yemen, and also enhanced its air bases in the Gulf from which it can launch drone strikes into the country.
Only last April, Washington launched a major drone attack which, according to the Yemeni government, killed at least two dozen militants. This is believed to have included foreign fighters in an al-Qaeda training camp in the remote mountainous area of Abyan.
Taken overall, while the central core of al-Qaeda has been diminished since bin Laden's demise, much of the wider terrorist network remains potent, including AQAP in Yemen. As world leaders have warned, dangers to international interests appear to be growing from threats fuelled by radicalised individuals returning from the Middle East with potentially greater terrorist resolve and capabilities.
Andrew Hammond is an associate at LSE IDEAS (the Centre for International Affairs, Diplomacy and Strategy) at the London School of Economics.