Going over a primary account of the fall of Constantinople by two witnesses for a college paper, I was surprised to see the authors claim that Byzantine men were forced by the Ottoman invaders to "fornicate with their hands or some other means" lest they be killed.
I did a little more research on the matter, and came across another claim, which states that the Sultan Mehmed demanded the grand duke of the city hand over his fourteen-year-old son for the sultan's pleasure, beheading both the duke and the boy when he refused.
Also in The Fall of Constantinople 1453 historian Steve Runciman states that Mehmed had promised his men the women and young boys of the city upon conquering it.
Basically I had no idea this sort of sexual abuse of men and young boys is said to have taken place after the capture of the city. Are there any more sources backing this up? Did similar things take place after other Ottoman sieges?
Follow-up questions. How likely is it that these were propaganda? What kind of propaganda would have been used against the Turks at the time?
Well, regarding the primary sources, you have to consider when they were written, for who they were written and why they are being written. The truth of the matter usually relies on who is writing for whom. If this was being spread in the European courts and being read then there is a good chance that these accounts are exaggerations made for some purpose probably to showcase how "evil" and "vile" the Ottomans were.
What sources does Runciman state for the passage you're referring to?