This tactic of letters is not merely the modus operandi of these militant islamists inspired by Zawahiri, it is their signature.
1	This	this	DET	DT	Number=Sing|PronType=Dem	2	det	2:det	_
2	tactic	tactic	NOUN	NN	Number=Sing	10	nsubj	10:nsubj	_
3	of	of	ADP	IN	_	4	case	4:case	_
4	letters	letter	NOUN	NNS	Number=Plur	2	nmod	2:nmod:of	_
5	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	10	cop	10:cop	_
6	not	not	PART	RB	_	10	advmod	10:advmod	_
7	merely	merely	ADV	RB	_	10	advmod	10:advmod	_
8	the	the	DET	DT	Definite=Def|PronType=Art	10	det	10:det	_
9	modus	modus	NOUN	NN	Number=Sing	10	compound	10:compound	_
10	operandi	operandi	NOUN	NN	Number=Sing	0	root	0:root	_
11	of	of	ADP	IN	_	14	case	14:case	_
12	these	this	DET	DT	Number=Plur|PronType=Dem	14	det	14:det	_
13	militant	militant	ADJ	JJ	Degree=Pos	14	amod	14:amod	_
14	islamists	Islamist	NOUN	NNS	Number=Plur	10	nmod	10:nmod:of	_
15	inspired	inspire	VERB	VBN	Tense=Past|VerbForm=Part	14	acl	14:acl	_
16	by	by	ADP	IN	_	17	case	17:case	_
17	Zawahiri	Zawahiri	PROPN	NNP	Number=Sing	15	obl	15:obl:by	SpaceAfter=No
18	,	,	PUNCT	,	_	10	punct	10:punct	_
19	it	it	PRON	PRP	Case=Nom|Gender=Neut|Number=Sing|Person=3|PronType=Prs	22	nsubj	22:nsubj	_
20	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	22	cop	22:cop	_
21	their	their	PRON	PRP$	Case=Gen|Number=Plur|Person=3|Poss=Yes|PronType=Prs	22	nmod:poss	22:nmod:poss	_
22	signature	signature	NOUN	NN	Number=Sing	10	parataxis	10:parataxis	SpaceAfter=No
23	.	.	PUNCT	.	_	10	punct	10:punct	_
