Decide that this small piece of land is perfect for a Hun foot hold messengers are send out to all the local Lords.
Your emperor has chosen death but you need not, join the Huns and your villages and cities will be safe defy us and we will do what Huns do best, don't be fools be alive.
As a warning the first villages that the Hun hordes come to are ransacked all the men killed all the women taken as wives or put in chains the childeren now in captivity will learn the ways of the Hun specifically the onogurs tribe and be inducted into its fierce warrior class as soon as they are of age.
The Hun forces stand ready to face any foe and give at local lords and pesants a day if they show supplication they are to paint the bow of a Hun on their door as supplication and the lords are to meet with Uldin to swear oaths of fealty.
Without the protection of the Emperor's armies, the local villagers are almost universally willing to cooperate fully with the occupying force, preferring to hand over supplies to the Huns than to lose their lives.
The occupying force may live off the land with little fear of popular resistance, though the longer the occupation continues the greater the hardship will be for the provincials.
In addition, Roman authorities will be unable to collect taxes from the province.
Uldin strode though the villa of contricuis the Roman Lord who he had come to speak to. As he entered the atrium he noticed the man standing there he was shaking very slightly but to his credit when he spoke it was firm and without a quiver in his voice.
"My lord Uldin great Khan" he said as he bowed "I am at your service as are my slaves and my villa" Uldin looked at the man he was not like any other Roman highborn he had ever seen he could see that the mans skin was tanned and that he had creases in his face from hard thought, hands that had clearly seen more than their fair share of work. "I have heard that you contricuis are the man to speak to you have governed these areas for ten years, during that time they have been the most prosperous they have been in two hundred years. While other areas falter in their pruduction you have kept yours in check. I can only assume this is due to you legion training." The gouvenor was taken aback he had not spoken of his time in the legion since he had entered these areas granted to him by the emperor and had no idea why a man so important as Uldin Khan would take such an interest in him. "But to get straight to the point I have come here to ask a favour of you. I wish you to teach my men the Roman art of siege warfare. When you are ready I will have one thousand of my men ready and waiting to be trained by yourself you will be the head dill master of this unit until your task is complete. As we speak I have every ex legionary within a hundred miles being brought here so that they might help you in this task. This is not a request but I have no experience in this area, because of this you will have as much coin as is needed and I will listen to any of your thoughts on the matter." Uldin stood there awaiting a reply. The shaking had stopped and the man was clearly thinking...
Contritus, a nickname given to a man who had been worn down over the years. It is said that he broke down, having survived too many battles and received too many non-fatal blows to continue as an effective soldier. He was allowed to return to his farm, and with the profit from a few slaves and savings over the years, he managed to deck the place out reasonably well. It was no grand palatial villa, but a new range had been added to the previously modest farmhouse, and now he enjoyed pretending to a higher station than his birth.
"You can call me Rufinus, for a start," he declared. "And so long as I can take a walking stick, I can show your men a thing or two. I am no engineer though, just an old veteran. I'm not sure how much I can teach you that you don't already know. Much have I seen, but little do I understand."
OOC: You can enlist the local populace to build siege works, and give a good go at taking Constantinople, but you can't magic up a wise man to make you better at sieges. You'll need help from a Roman army or prolonged contact with Roman engineers sent by a friendly Roman faction before you'll benefit from Roman engineering.
The Huns did lay siege to cities successfully, but even Aquileia took a long time, and Attila may have considered giving in and heading home. I'm afraid that short of Roman allies, or a Hunnic warfleet, there's nothing that can help you take Constantinople other than a concerted and determined effort. It may take years, cost many lives, and be unpopular, but such is the price you must pay if you want to take the Queen of Cities.
Taking the city is, of course, optional. If you can control the straits at Gallipoli you can cross over to Asia. All you need is to out-boat the Romans, or get them to agree to safe passage.
The man seemed determined and despite his lack of knowledge on the matter that Uldin was interested in he liked the man. "Thank you Rufinus and so long as we have an understanding your household shall be left alone and when we do eventually take Constantinople I can promise that you will benefit greatly from your decision here today" with that Uldin strode away and rode back to the hunnic camp. The Hun army never stayed still for long and there was a need for bloodshed and glory building within the ranks.