‘Parthia is a great empire,’ Crispinus said, like a schoolmaster bringing an unruly class to order. ‘Indeed, it is the only kingdom beyond our borders worthy of the name of empire. You should all know enough history to realise that fighting the Parthians is no light matter, for when well organised and well led they are formidable indeed.

‘Yet they are not well led, not at the moment. Their royal family breeds more prolifically than the Armenians, so there are always plenty of princes, and too many heirs naturally produces conflict in a people whose laws and customs are so loose. At the moment there are three kings in Parthia – or at least there were at the last count and who knows, by this time another may have popped up for all we know. Thus their main efforts are devoted to warring with each other, which is good from our point of view. On the other hand, the desperate times of civil war make them unpredictable. They may do something rash, and even if they do it with less force than would be the case if they were united, still it could be dangerous because it would be unforeseen. So Caecilius is perfectly correct to point out that we are in the path of any likely invasion, should it come from the south. There is no sign of trouble from that direction at present, but we must never forget that it just might happen.

‘We are the only legion at full strength left in the region. The good news is that we are getting some more auxiliaries attached to us, so that soon we shall have a very handsome little army, very handsome indeed. It will be up to us should they come.

‘But…’ Crispinus dragged out the word to get their attention. ‘But I do not think that such a contingency will arise, not this year, at least. Still, the very uncertainty of power within Parthia causes problems in itself, for it is bound to spread. We guard our empire by strength. Those living outside must fear that strength, just as they trust our faith not to abuse them if they behave properly. Here we deal with kingdoms.’ Crispinus tapped with the stylus once more. ‘Closest is Osrhoene, then Adiabene and others beyond.’ The map quickly grew vague and was tightly compressed to squeeze the names and principal routes and cities into the little space left outside the provinces. Crispinus grimaced. ‘Let us change to something better. Arrian, dear fellow, if you could be so good as to unroll the next map. Thank you. That’s better, much better.’ He helped the tribune weigh down the scroll which kept wanting to fold up.

‘Osrhoene is just beyond the river. Its kings rule from Edessa, and on the whole they are usually friends of ours, more or less, but do not require our seal of approval on their power, and it has to be said they have always been closer to the Parthians. That is the root of the problem now. Old Abgarus is trying to pick the winning side when it is not obvious to anyone who that will be. So he is keeping his distance from us. He sent his son with an escort to see Trajan, but had only empty words and no promise of loyalty, let alone agreement to let us have some troops for the coming campaign. What do you know of their warriors, Caecilius?’