What event was the most significant in damaging the strength of the byzantine empire during the crusades

From this excerpt of the prologue of the Corpus Iuris Civilis, what departure from older Roman traditions is clear? The laws show that the empire has developed a bureaucracy that makes normal soldiering unnecessary. The law now honors Christianity as a central part of the Empire's existence. The law explains that the Roman Empire is using war to spread Roman ideas. The law has replaced old social class divisions with an egalitarian church.