But see that cannot be a reason because during the late 4th and early 5th century the Eastern Army was nothing... it barely had troops to fight brigands and bandits... it did not repeal any barbarian or Persian incursion until the 6th century well after the West was gone... the East survived because it used diplomacy and because the civic administration controlled the army unlike the west where the generalissmos control the army and not the emperor. Besides, the West had a better army which for a time had most of what remained of the Eastern Army as well. The West continued to grow in force of arms, while the East followed a policy of culling thier ranks, killing successful generals etc, because they feared a strong army under one man who would dominate Constantinople... when the Huns invaded, the East sat behind their high walls... when Isasurians went on rampages in Asia Minor... they sent little forces barely capable of doing the job to stop them and half the time they could not contain it. So... if the East survived by added abilities, it was surely not the military... not until the very late 5th early 6th did that army become a potent force.
Wait, how did thw West supposedly grow in force of arms when in fact it crumbled to nothing?