Thanks to Antoine for some interesting questions. Of course, I have to a certain extent elided objects and buildings through the use of the phrase 'built objects'. It is only right to ask whether I'm somehow inconsistent to suggest that there's something special about buildings that make them different from objects more generally. I think I'd be happy to concede that in the book I equivocate on this slightly. In the conclusion of the book, I speak a little to this question (p.129) and note that there might be two reasons to think of buildings being different from objects more generally.

• On the one hand it's difficult to think of cases where annihilatory violence has been focused on objects more generally. Iconoclasm might be a case (as might burning books) but such a case can be understood under the rubric of the destruction of cultural heritage anyway. So, buildings seem to be a significant class of objects insofar as they have the dubious distinction of being the object against which it is easiest to see annihilatory violence being directed.
• On the other hand, and more importantly, I would say that objects are not all ontologically identical – that is, different types of object do different things in the world. At the risk of simplifying things too much, buildings are different from hammers. Why are they different? Here I would argue that buildings have the characteristic of providing a point from which we can understand our location in the world. That is to say, if I pick up a hammer I can understand that I am about to take up a particular position vis a vis a piece of wood or a picture hook. But if I stand in front of a building (or indeed, inside) I understand something different, namely where I am in a terrain and, more importantly, that this terrain is, in principle, home to others. I think this is the reason why I see buildings as different to objects.

With regard to the heterogeneity of the urban/architectural form, I would want to point out the amount of work that is done in modernity by those who seek to exclude certain classes of subject from their buildings. Whether it is carving impressive columns, erecting steel gates, making benches hostile to rough-sleepers or disguising residential properties in up-scale neighbourhoods, what is most noticeable about these attempts to reserve architecture for a homogeneous class of subjects is the sheer amount of work they have to put in to achieve this. I have always interpreted this as a tacit acknowledgement that buildings are first and foremost public objects, and thus always already admit of the possibility of heterogeneity. It's against this prior heterogeneity that architects try to work (mostly unsuccessfully) to effect forms of exclusion.

Now, with regard to nomad societies: I’m afraid I will dodge the question by saying something else, which I nonetheless think is relevant. Urbicide is not meant to be a trans-historical and universal account of all forms of violence against objects and/or buildings. On one level that is obvious, but on another I realise the close kinship of urbicide and genocide means I run the risk that all genocide scholars must confront of the indefinite stretching of their conceptual lexicon. Just as every victim seemingly wants to claim that the violence he or she has suffered is a case of genocide, I am aware that there may be attempts to try to stretch urbicide to cover a multitude of events. I have to say that urbicide may well not cover violences encountered by nomads. I don’t know if that diminishes its conceptual and political force. I’d be interested in hearing your thoughts on this.

You're right that this is a concept built out of the analysis of ethnic-nationalist violence. It thus works well in cases where evidently plural societies are faced with a form of violence predicated on homogenisation directed from within that society, not from outside. It is easy to understand that self-consuming logic of destruction that urbicide comprises, in cases where one element of a given social constellation is trying to deny its connection to other elements of that social constellation. On first glance that might seem to rule out inter-state conflicts as offering instances of urbicide. But I would argue (as I do in my account of Chechnya) that this is a matter of scale. Insofar as Allied air power projected itself as having global reach, we might regard Japanese or Axis cities as presenting a principle of difference within a world–wide social constellation - and thus we might include the bombing of Dresden or Tokyo in the rubric of urbicide. That said, I also note in the book that urbicide does not replace genocide (indeed both may occur simultaneously) and I might prefer – as others have done – to see both of these latter cases as instances of genocidal, or degenerate, warfare.