Julian II (the Apostate) and his policies

[Theodosius the Great]

A dynastic succession alone is not a guarantee for stability.

True. Then again, what is ?

If you have a child as leader, the quarrel among the advisors can easily lead to disaster.

Yes, but my point is that even in those circumstances the Empire was still more stable, politically speaking. At least the Empire's energies are less directed internally against domestic enemies.

The problem was that the Roman emperors could not easily refer to some of the reasons which may make a monarchy more stable (being a God, Gods vice governor on earth or with Gods will at least for example). The Christian propaganda needed some time to come to effect.

Again, I see it differently. Christianity seems to have been an instant sauces in stabilizing the Empire. The legions never rebelled against an established Christian dynasty. How many pagan dynasties could boast that ? Even the 5th century "generalissimos" never attempted to seize the Emperorship from a dynast.

In my opinion military, political, economical and social factors can not be seen isolated.

You're right. There's the social aspect that accompanies the military explanation vis-a-vis the decline of the West. I see that Rome was the victim of its own success. After conquering the bulk of Western Europe the Empire was able to accelerate the Romanization of its subjugated populations. Soft living eventually sapped any remnants of virility among the provincials who once provided vital warrior stocks to be tapped for legionary recruitment.

I'm not sure if that's what you mean by a "positive attitude towards the state" that Late Romans lacked. If it is then I think its unfair to attribute that attitude solely to Late Romans. It was common during most of the Imperial period as opposed to the Republican period.

Rome had seen enough disasters worse than Adrianopel before and she was able to manage.

The last disaster to be seen on such a scale was the Battle of the Teutoberg Forest, 360 years earlier. That was a different time and a different world. Even Augustus didn't have the kind of manpower reserves available to him that the Republic enjoyed during the Punic Wars. He had to resort to conscription and suffered a backlash for doing so. Later Emperors in the fourth century had even more trouble pressing civilians into the army.

Consequently, after Adrianople, the Visigoths were seen as a new pool of warriors to be tapped by the Emperors to be recruited into Roman service. They became indispensable despite the debilitating effects of their de facto independent status.

A disaster like Adrianople almost happened 15 years earlier due to Julian's shoddy generalship. He got his army stuck in a tight spot. His incompetence managed to sever his troops from their supply lines and he compounded the fiasco by failing to capture Ctesiphon. Only 60 years earlier Galerius had managed to capture and sack it. And before him Septimius Severus, Marcus Aurelius and Trajan did the same.

~Theo