It is important to resist the temptation to dismiss all these tactics as self-serving, self-justifying and Machiavellian. Had the Byzantines been less so, European history might have been greatly changed.
Byzantine diplomacy was crucial not only in preserving the Byzantine Empire, but in preventing the Islamisation of Europe. Without this outpost of Christendom deflecting the Muslim tide from the seventh century to the fifteenth, it is unlikely that Western civilisation as we now know it would have endured. By the time the Ottoman Sultan Mehmet II took the city of Constantinople by assault in 1453 and renamed it Istanbul, the states of Eastern Europe had absorbed enough Byzantine culture (and diplomatic technique) to stand on their own. The walls of Constantinople and the imperial diplomats gave the fledgling Christian religion 700 years to grow and prosper.
Excerpts from an article by Michael Antonucci, published in History Today, Volume 43 / 2, February 1993.