On Sep 8 2011 on CNN television, following President Obama's speech, a breaking news item was broadcast concerning a "New Terror Threat for 9/11 Anniversary."

The news item claimed that "Anniversaries are significant to Al Qaeda." I have heard this claim repeated in the past.

But is this true? Have any previous attacks (worldwide) by Al Qaeda occurred on an anniversary -- either an 'obvious' date like 9/11 or an anniversary significant to the terrorists culture or goals?

  • 4
    This can be re-written as "Are anniversaries significant to [people]?" and be just as significant. The group could decide at any time that it would be tactically wise to try some other dates, but they haven't because they are people (albeit not necessarily ones you'd want to have over for tea). Sep 9, 2011 at 1:39
  • @dmckee Many people commemorate dates of significance, be they national holidays, personal holidays, religious, with appropriate festivities. The context of the news article changes the significance. The question isn't whether terrorists celebrate defeating US defenses in their camps every 9/11 -- to the extent it is a managed group it is whether they form a plan to go out and kill some more people on that date.... or some other specific date. Lone wolves could also plan... As you hint there is a game theoretic problem of monitoring and evasion offset by other concerns.
    – Paul
    Sep 9, 2011 at 3:18
  • Media hype, when attached to sentimental emotions, may get a lot more attention from the audience (and more attention equates to higher ratings). Sep 9, 2011 at 19:59

2 Answers 2


Yes, specific dates have special meanings to organizations such as Al Qaeda, Hezbullah, etc. (Basically anyone as noted by dmckee in the first comment to your question.) The Congressional Research Service has even written a document about this (PDF). The National Counterterrorism Center also has a great deal of information online (although I find that interactive timeline severely lacking).

The United States Air Force considers the significance of dates to terrorists important enough to release something in an unclassified forum.

Terrorists often pick meaningful dates to schedule their attacks. The biggest terrorist anniversaries of the year, however, are April 19 and 20. These dates are extremely significant, especially to domestic terrorists.

Granted, a great deal also spoke about Domestic terrorists. This behaviour is not restricted to Islamic terrorists, but pretty much any radical that has a specific message to convey through violence. It "heightens the impact" as it were.

The Department of State offers this

In the past, terrorist organizations have on occasion planned their attacks to coincide with significant dates on the calendar.

Keep in mind, most assessments and documentation for this sort of intelligence activity is classified either because the sensitivity of the source, or to keep those who would do harm guessing as to exactly what we do know. Documentation will be difficult to find, and unless you restrict your search to specific veins, you may come up with some incredibly irrelevant, not to mention outright wrong, data.

Some additional reports that may aid you in learning more:

Terrorist Motivations and Behaviour (PDF)

Counterterrorism Calendar 2010 (PDF)

  • 1
    There is a risk here: that post-hoc analysis of the significance of the date, with no limits to how far back or how significant the event can be, will - I claim - always be able to find some significance to any date. I'm pondering how you might test the claim without classified data (e.g. look at a plot of every terrorist attack/plan and see if the dates are distributed more than just randomly - seasonally adjusted - that won't work if, for example, all attacks are on the 1st anniversary of some (non-terrorist) event.)
    – Oddthinking
    Sep 9, 2011 at 1:42
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    @Oddthinking Sadly, that gets into seeing classified documents that quote the planners (both in cases of stopping an attack before it happens or capturing them after) saying something to the effect of "To take vengeance upon the infidels who convicted Immam Soandso on April 12th, we will have Jihad on that day." (NOT an exact quote, but you get the idea.) I'll see if I can dig up any sort of unclassified data on this though. Page 7 of the Terrorist Motivation PDF mentions anniversaries as well. Sep 9, 2011 at 1:56
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    @Paul, September 11, 1972 - Munich Olympic Games massacre is a pretty ideological anniversary. Sep 9, 2011 at 12:27
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    note also that, at least with our calendar system, there are really only 366 choices. The odds of an alignment of meaningless coincidences is extremely high.
    – horatio
    Sep 9, 2011 at 17:08
  • 2
    @Paul, as one IRA operative/terrorist once said, "In order to stop us, the authorities had to get lucky every time. For us to succeed, we only had to get lucky once." I hope you are right that nothing does happen, but keep in mind that we normally don't hear about all the thwarted efforts. Sep 10, 2011 at 16:13

11 September 2011, two days after Paul asked this question, the later Boston Marathon bomber, Tamerlan Tsarnaev, killed three Jewish men. Only 3 other deaths of Americans due to terrorism worldwide were reported in 2011.

11 September 2012 US ambassador Chris Stevens and 3 other Americans were killed in attacks in Benghazi, Libya. Only 8 other deaths of Americans due to terrorism worldwide were reported in 2012.

  • Anecdotes aren't data. Are these more common than other dates?
    – Oddthinking
    Feb 1, 2017 at 15:00
  • @Oddthinking I added more information. The 9/11/11 murders represent half the terrorism deaths of Americans worldwide in 2011 and the 9/11/12 deaths represent one third of terrorism deaths of Americans worldwide in 2012.
    – DavePhD
    Feb 1, 2017 at 15:25
  • @DavePhP : The Waltham triple murder of 2011 doesn't qualify as a terrorist attack. It is a murder, only linked to terrorism because the main suspect proved to be a terrorist two years later. According to the START document you linked, there has been 0 fatalities in the US in 2011 because of terrorism, and 3 worldwide. As a guess, I would say that the anniversary may have being meaningful for the Benghazi terrorists, but probably not for the Waltham murderer(s).
    – Evargalo
    Aug 10, 2018 at 7:51

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