There are several reasons why the Byzantine Empire survived for nearly 1000 years despite outside threats.  First, the Byzantine emperors were very strong and had absolute power. The support of the Byzantine Church reinforced the strength of the emperor.  The government and military of the Byzantine Empire were backed up by an effective group of administrators. Besides having a strong effective government, the Byzantine army and navy were also very skilled.  The Byzantine Empire was divided into military districts ruled by a general who answered to the emperor.  Soldiers in the district armies received land as payment.  Fighting for the land on which they lived gave them added incentive to be loyal and brave.  The military leaders were very capable and led highly trained troops.  Military techniques were advanced.  They used mirrors to flash signals for attack and retreat, and a medical corps was established to care for the wounded.  The Byzantine navy also was very powerful. In one campaign against Crete, 1330 ships were launched.  The navy used “greek fire”, a combination of sulfur and naphtha that could burn ships on the water.  Finally, the Byzantine Empire had a stable and thriving economy, with Constantinople becoming a center of trade and manufacturing.  This brought wealth to the empire which helped pay for the expense of defending the empire against its enemies.