When did the Roman Empire fall (your thoughts)?

[Flavivs Aetivs]

When Attila marched on Rome he was intercepted by Pope Leo along with other officials to dissuade another sack of the defenseless city.

I think that Leo's 'interception' of Attila is a twisting of events to fit later Christian propaganda. If you look at the chronology and the places mentioned it's more likely that Leo was sent to act as an emissary when Attila was already withdrawing from Italy.

Agreed, Attila withdrew because of lack of logistical support - he didn't have the logistical capabilities to supply on the long term, and his men suffered disease and lack of food because of it. Couple that with Aetius' harassment of the Huns with the western and eastern field armies, and Marcian's campaign on top of that, and Attila had no choice but to withdraw.