[peace4all]

True for complex systems, but West Roman empire didn't "collapse" instantaneously, nor within a year/decade.

If I remember correctly what I read on it, the actual date is arbitrarily taken for didactic clarity, and it's the date the capital moved to another city. But the kingdom still called itself Roman, so contemporaries didn't quite notice the difference. BTW, this is how modern Romania got its name -- smaller kingdoms in the former empire called themselves the glorious Rome.

The curious detail is that Barbarian leaders actually wanted to become king of Rome and to be acknowledged as equally civilized, rather than merely sack and loot it. Some of them were actually legioneers, if I remember it correctly. So it's not clear if a legioneer sacked Rome and set himself as king, was the new state still Roman or already not.