As discussed in class, the Byzantines used a variety of methods to defeat their enemies, and weren't afraid to use "any means necessary", including bribery, assassination, alliances, spies, terrorism and other forms of diplomacy and military action to survive.
Be sure to take a look at the Byzantine maps tonight for homework, and get a good handle on what parts of the world the Byzantine Empire included at their height, as well as during their decline in the 1400s.