What were the most impactful traitorious decisions made during the history of the Eastern Roman Empire?
John Katakouzenous VI making alliances with Serbia and the Turks to win against the Regency of John V Palaiologos but ravaging the Eastern Roman Empire beyond repair takes the crown but there are honorable mentions.
>Alexios III requesting aid of the Sultanate of Rum to attack the Nicaean Empire just because Theodore Laskaris rightfully refused his authority.
>Andronikos IV Palaiologos giving Gallipoli to Murad I and the Ottomans, allowing him to easily attack not just the Empire itself but also the rest of Eastern Europe.
I'd like to know if there are more incidents in Eastern Roman History beyond these.