Although attendance numbers are down, Catholicism is still deeply entwined in the national fabric of France, and the attack has already led to outrage across the country.
The goal in going after such a provocative target? To trigger a backlash against Muslims in France and drive the country's Muslims into the recruiting arms of the Islamic State.
The attackers filmed the atrocity, a nun who managed to escape told CNN affiliate BFM.
According to French President Francois Hollande, the attackers claimed they were acting on behalf of ISIS, something the group also claimed via an affiliated news agency.
A French intelligence source told CNN's Christiane Amanpour that one of the attackers had been radicalized after the Charlie Hebdo killings and had tried to enter Syria on two occasions and was associated with Maxime Hauchard, another French jihadi
who appeared in an ISIS beheading video in 2014.
In recent weeks European intelligence services have detected a significantly expanded effort by ISIS operatives in Syria and Iraq to directly reach out to extremists in Europe to encourage them to launch attacks. European counter-terrorism officials believe the group is trying to project an image of strength and unleash vengeance, as it loses ground in Syria, Iraq
and Libya. This month has already seen ISIS supporters in Europe launch two attacks in Bavaria
and a deadly truck rampage in Nice.
ISIS 'aiming to stoke backlash'
ISIS listed French churches as targets in the fifth issue of its French language magazine which came out last summer "to create fear in their hearts."
In April 2015 French police thwarted an ISIS directed plot to attack a church in Villejuif
in the Paris area after the operative recruited to launch the attack -- Sid Ahmed Ghlam, an Algerian student in Paris -- accidently shot himself in the leg. Ghlam had twice traveled to Turkey where he met French ISIS operatives linked to Fabien Clain, a senior French ISIS member
who later is believed to have helped mastermind the November 2015 Paris attacks.
In urging attacks on churches, ISIS is trying to eliminate what it calls the "grey zone" for Muslims in the West by provoking a far-right backlash. A drumbeat of attacks in France has led to a groundswell of anti-Muslim anger, which is being stoked and exploited by far-right politicians.
According to France's National Human Rights Commission (CNCDH)
there were 429 anti-Muslim threats
and attacks in 2015 -- a rise of 223% from the previous year. Marine Le Pen, the leader of France's far-right national front, reacted to Tuesday's atrocity by renewing calls for fundamentalist mosques in France to be shut.
ISIS declared an all-out war on Christianity when its fighters beheaded 21 Coptic Christians near Sirte
, Libya, in February 2015. "You have seen us [in Syria] chopping off the heads of those carrying the cross [and now] we will fight you altogether," a masked fighter with a North American accent stated in gruesome video featuring waves of blood flowing northwards into the Mediterranean. The message could not have been clearer: the "Crusader" enemy and all Christians were now seen as one and the same, and all needed to be exterminated.
ISIS campaign branded genocide
In March the U.S. Secretary of State John Kerry characterized the ISIS campaign against Christians and minority religions in areas under its control as a genocide
Not only has the group driven out Christian populations from cities such as Mosul, but it has targeted them for death across the Middle East, including in Egypt where a local Islamic State affiliate has assassinated Coptic priests. In Nigeria, ISIS affiliate Boko Haram killed more than 4,000 Christians last year and attacked almost 200 churches
, according to figures compiled by a Nigerian Christian organization.
Also in March, suspected ISIS militants in Yemen carried out an attack on a Catholic retirement home in Aden killing 16
-- and a Pakistani Taliban splinter group which has been supportive of ISIS targeted Christians in an Easter attack in a park in Lahore
, killing 69 people.
It turned out most of the victims in the Lahore attack were Muslim, as were a third of those killed in the Nice truck rampage earlier this month, exposing ISIS to potential criticism among jihadis that it is shedding the blood of Muslims.
By going after churches, ISIS and its supporters are singling out Christians, and trying to usher in a new war of religions.