When did the Roman Empire fall (your thoughts)?

[Theodosius the Great]

Yes, Tours preceded the HRE, but the threat did not end afterwards. Clearly, Charlemagne felt the need to create the Spanish March. Then the Umayyads established themselves in the Iberian peninsula for over 100 years and became a bigger threat given their expansionist bent.

As for the Turks, I qualified my statement by saying "western Christendom" and "later". The Turks eventually reached the gates of Vienna - twice, I believe.

~Theo