Most westerners know that Islamist extremists would love to strike a blow at its heart. But few are so tantalising a target as Paris.
The answer is that France is fighting jihadists all over the world; and has one of the largest Muslim populations in Europe – and arguably the most divided society. It also has a steady stream of guns pouring in from across continental Europe's porous borders. It is a potent, explosive mix – as shown by the Charlie Hebdo attacks of January, and now the Paris shootings.
"This is for Syria," one of the Paris attackers reportedly said. But he could have said it was for Mali, or Libya, or Iraq.
Indeed, France takes pride in its proactive stance against Islamists worldwide, especially in the face of what is frequently seen as British and American retreat. Over 10,000 French troops are currently deployed abroad – over 3,000 in Western Africa, 2,000 in Central, and 3,200 in Iraq.
French intervention in Mali, against al Qaeda in the Islamic Maghreb, in 2013 was seen as pivotal in the weakening of the jihadi group. A fortnight ago a leader of an AQIM affiliate urged his followers to attack France in retaliation for their presence in the region.
And last week President Francois Hollande announced that France will deploy an aircraft carrier in the Persian Gulf to assist the fight against the Islamic State in Iraq the Levant (Isil), setting him on a collision course with the Islamist leaders.
A key problem, however, is internal.
The feelings of isolation and exclusion can be overwhelming, with few high profile Muslim role models in business or politics. France's stridently secular state, the banning of the burka and the power of the Front National have not helped to ease tensions between communities.
Mohamed Merah, the Toulouse shooter of 2012, grew up in a tough suburb of paris, began as a small-time delinquent, was sent to prison, and emerged a hardened jihadi with "meaning" in life.
Mehdi Nemouche, author of the May 2014 murder of four people in Brussels, was also radicalised in prison – travelling to Syria when he was freed and then coming back to attack the Jewish museum.
Chérif Kouachi and Amedy Coulibaly both followed a similar trajectory of lack of opportunity, descent into criminality, prison and radicalisation.
Inside France's prisons, 70 per cent of the inmates are estimated to be Muslims – by law, France cannot ask a person to state their religion, so official data is unavailable. In England and Wales, by comparison, Muslims account for 14 per cent of the prison population, according to Home Office statistics, and five per cent of the population nationwide.
In the aftermath of the Charlie Hebdo attacks The Telegraph reported how France was struggling with radicalisation inside its prisons, and unlike Britain had very few Imams to enter the cells, and limited de-radicalisation programmes. In April Rachida Dati, the former justice minister and now a special rapporteur on radicalisation, told this paper that France was not doing enough to fight the power of Islamist radicals behind bars.
And another constant source of concern for the French authorities is the ease with which weapons can be trafficked into France.
Belgium has long struggled with illegal arms; it is believed the Charlie Hebdo attackers sourced their weapons there. The Balkans are also favoured shopping destinations; the years of conflict there during the Balkan Wars have left the region awash with cheap, nondescript weapons.
The result is a powder keg atmosphere. And French were not completely unaware of the fact.