Why CIA’s operation directed to suspicious people associated with terrorist group is called “Signature strike”?

Question

There was the following article in the Time magazine’ (February 11) titled “Drone home,”

“According to reports in the New York Times and elsewhere, the Obama administration conducts so-called signature strikes, which are aimed not at specific high-level targets but at any person or people whose behavior conforms to certain suspicious patterns."

I understand that what “Signature strike” means with the line modified by which clause after the words, signature strikes in the above article and with the following statement in the Wired (11/04/11)

The CIA is now killing people without knowing who they are, on suspicion of association with terrorist groups. The article does not define the standards are for “suspicion” and “association.” Strikes targeting those people — usually “groups” of such people — are called “signature strikes". –wired 11/04/11

I’m curious to know the etymology of “signature strikes.” I mean, why CIA operation aimed at any suspicious people who are judged to be associated with terrorist group is called “Signature” strikes?

OALED defines “signature” other than 'your name as you usually write it at the end of letter'as:

1. the act of signing sth.

2. a particular quality that makes sth different from other similar things and make it easy to recognize.

I can’t relate either of the above definitions to the definition of “signature” strikes given by both the Time and the Wired.

Answer 1

The New York Times explains the origin and meaning of the term signature strikes here:

But for several years, first in Pakistan and later in Yemen, in addition to “personality strikes” against named terrorists, the C.I.A. and the military have carried out “signature strikes” against groups of suspected, unknown militants.

Originally that term was used to suggest the specific “signature” of a known high-level terrorist, such as his vehicle parked at a meeting place. But the word evolved to mean the “signature” of militants in general — for instance, young men toting arms in an area controlled by extremist groups. Such strikes have prompted the greatest conflict inside the Obama administration, with some officials questioning whether killing unidentified fighters is legally justified or worth the local backlash.

Answer 2

The second definition is the applicable one. A target can have a signature, referring to its distinguishing characteristics. A related technical term is infrared signature. In a more general sense, for example, a person's signature could take into account things like gender, height, weight, the way they walk, the car they drive, etc. So a signature strike is striking against something based on its signature, rather than a more definitive identification.

Answer 3

The term "signature strike" is consistent with other military techno-jargon, such as the activity known as "Measurement And Signature Intelligence (MASINT)", which is described in wikipedia.

In that example, "signature" refers to distinctive characteristics. Distinctive characteristics do not have to be unique, but they are considered sufficient to alert to a particular thing (or class of thing) of interest. Signature intelligence leads to signature analysis, which leads to signature strikes.

In its initial meaning, for example, a particular vehicle may be determined to be the signature (a distinct indicator) of a terrorist. Later, according to the quoted story, what constituted a signature was made broader and apparently has become less distinct ("a bunch of men with guns").

There is really nothing purely military in the meaning, though. It comes from the common meaning of the word "signature", used as an adjective. For example "signature move" as in "The moon walk was Michael Jackson's signature move." A recording artist may have a "signature song".

Answer 4

The earliest example I found in Google News of this type of "signature strike" is in an article in ("Pakistan's oldest and most widely read English-language newspaper") Dawn on May 20, 2011. It quotes a US embassy cable released by WikiLeaks:

Government official urged follow-up drone strikes

KARACHI: In a cable sent on October 2, 2009 the US Peshawar Consulate’s Principal Officer Candace Putnam reported on discussions with a high-ranking FATA Secretariat officer on September 30 about an imminent military operation in South Waziristan. When asked if the bureaucrat – who coordinates closely with the army – thought the army had enough troops to take on the operation, he responded “after a long pause” that “the Army thought they had the capability and that the US could assist with continued strikes.”

The FATA officer, in fact, went further, urging the US to do follow-up strikes immediately after initial attacks. “He explained that after a strike, the terrorists seal off the area to collect the bodies; in the first 10-24 hours after an attack, the only people in the area are terrorists,” writes Putnam, then quotes the FATA officer as saying “you should hit them again-there are no innocents there at that time.” The official also “drew a diagram essentially laying out the rationale for signature strikes that eliminated terrorist training camps and urged that the US do more of these.”

Cable Referenced: WikiLeaks #227969

They link to the [redacted] text of the October 2, 2009 memo:

1. (S) XXXXXXXXXXXX remains a strong advocate of U.S. strikes. In fact, he suggested to PO that the U.S. consider follow-on attacks immediately after an initial strike. He explained that after a strike, the terrorists seal off the area to collect the bodies; in the first 10-24 hours after an attack, the only people in the area are terrorists, so “”you should hit them again-there are no innocents there at that time.”" His sources report that the reported September 29 strike in South Waziristan had been particularly successful; “”you will see that you hit more than has been reported in the press both in terms of quantity and quality.”" XXXXXXXXXXXX also drew a diagram essentially laying out the rationale for signature strikes that eliminated terrorist training camps and urged that the U.S. do more of these.

This is also the only example found searching the cables database directly.