As we point out in our Course on “Terrorism Studies” at Police Science Institute … historically through present-day, terrorist groups very often selected important dates of prior victories, dynamic events or even birthdates of terror leaders when selecting the “perfect time” to launch a terrorist attack.
Nationalist groups may strike to commemorate battles won or lost during a conventional struggle, whereas religious groups may strike to mark particularly appropriate observances. Many groups will attempt to commemorate anniversaries of successful operations, or, the executions or deaths of notable individuals related to their particular conflict.
Likewise, striking on days of particular significance to the enemy can also provide the required impact. Since there are more events than operations, assessment of the likelihood of an attack on a commemorative date is only useful when analyzed against the operational pattern of a particular group, or, specific members of a group's leadership cadre.
The fact that “Friday the 13th” was chosen as the date ISIS attacked six soft-target locations in Paris, killing nearly one hundred thirty and injuring over three hundred, might not have been by mere chance. That day represented a historical edict by the King of France leading to the effective eradication of the Knights Templar.
As recounted by author Katharine Kurtz in Tales of the Knights Templar (Warner Books, 1995) … “on Friday October 13, 1307, a day so infamous that Friday the 13th would become a synonym for ill fortune, officers of King Philip IV of France carried out mass arrests in a well-coordinated dawn raid that left several thousand Templar — knights, sergeants, priests, and serving brethren — in chains, tortured, and, executions by burning at the stake”.
That event represented the decimation of the Knights Templar … the "warrior monks" formed during the Christian Crusades in order to combat Islam. Renowned as a fighting force for two hundred years, by the 1300’s, the order had grown so pervasive and powerful it was perceived as a political threat by kings and popes, and, deemed an arch enemy of Muslims.
Was the November 13, 2015 Paris terrorist attack by the Islamic State an eight century-old remembrance ?