Marcus Aurelius\' function on the Danube

[Iosephus]

Avete,

I agree with the previous posts, plus I think there is one more thing to consider: the personality of MA.

If his own memorials are true then there are two more factors:

1. MA was a stoic philosopher who disliked the intrigues and servility of his own court in Rome, thus he could see the war as a possibility to "flee" from his decadent and turncoat courtiers
2. MA had a very strong idea of duty and honour. He could think that if his Empire is in need, then he, as the Emperor, had the duty to be there where the situation is the most dire (on the frontline).

Just my two cents!