They have also fought one another over long-held regional enmities; the most recent such battle occurred last month.
Two years after a national reconciliation that followed a devastating civil war, Tajikistan is still a land of clan-based paramilitary forces, Islamic revivalism and regional enmities.
The besiegers have shied from all-out assaults, for fear of killing civilians and deepening regional enmities.Some say the delay reflects fears within the National Transitional Council, the 43-man proto-parliament under Mr Abdul Jalil, that the end of military fighting might herald the onset of harsher political skirmishing.
Or after some initial air strikes will things in due course simply revert to "normal", and the old, obstructive regional enmities return?
This is where Shahzad's case enters the broader immigration debate, for with the mounting numbers of legal and illegal aliens to America, and the complexity of regional enmities that we import, we face a host of ugly triage decisions.
How will the seeming political stalemate of regional hatred and enmity shape them in new ways?
While the agreement stops short of Serbs recognizing Kosovo's independence, it has been hailed by the European Union, which brokered it, as a breakthrough that can help overcome ethnic enmities, bring regional stability, enhance economic development in two of Europe's poorest countries and help clear the way for them to join the union.
Both of them, and Saudi Arabia, should do more to develop this opening into serious regional diplomacy across lines of enmity.
The GIA, in particular, has been linked to attacks in the mid-1990s on the Paris metro system, the GSPC to plots in Europe and North America prior to the attacks in New York on 11 September 2001, and the groups across North Africa have historically felt particular enmity towards former regional colonial power France.
The chance of Iran agreeing to a Saudi deal was never high, not least given a history of enmity between the two regional rivals – most recently over Syria – as much as oil politics.
