If the last, by what kind of gifts?
Has it any enemies, and if so, who are they?
What were its origins? What is its history? What is its climate and its geographical position?
Has it usually been a friend or an enemy of the Byzantines? Trace this back to the day when it first appeared on the scene!
With this information—the questions had been carefully worked out by the emperor Constantine Born-in-the-Purple in a book called How To Run the Empire—the Byzantines could select the right method for the nation they were interested in and then go to work on it.
If the ruler or his ambassador was easily dazzled, they could impress him with court ceremony and with purple shoes and robes, and they might even give out a title or two such as patrician or archon. They might even take some northern duke or count and promote him to be prince or king provided he swore allegiance to them.
If he was greedy and avaricious—and, said Constantine, “the tribes of the north demand everything and hanker after everything”—they could give him cash in hand or even pay an annual tribute.
As a last resort, the emperor could marry a foreign princess or give a sister or a daughter in marriage to a foreign prince. The Byzantines did not really approve of the latter, especially the ladies who were shipped off to some outlandish country without Byzantine comforts or conveniences! “I am being sacrificed to the wild beast of the West!” wailed one of them. But it often worked wonders. From distant Asbagia under the towering snow-crowned Caucasus Mountains to distant Germany, where the “wild beast of the West” lived, many and many a kingdom was made friendly to the Byzantines because a Byzantine princess sat on its throne.
But of course when an emperor did this, he must never give the barbarians all they asked for, and he must always think up a good reason for not doing so. If they asked for an imperial crown or an imperial robe, he must point out that these were sacred and consecrated and tell of the horrendous death suffered by one emperor who had given some to his Khazar relatives. If they asked for Greek fire, he must tell them that it was given by an angel and that anyone who gave it away would be struck down from heaven. If they sought to marry a princess, he must tell them that the demand is monstrous, even though the royal robe-makers were already embroidering the wedding gown.
In that way he would not only save some of his valuable possessions, but the barbarians would appreciate the ones he did give them all the more.