The detachment led by Iulianus was first to arrive at Sirmium.
He decided not to wait for the two other detachments to arrive and headed south to Naisus to winter.

Four weeks later a messenger arrived from Constantinople telling him the Augustus Constantius was dead and the armies of the East recognised Iulianus as the new Augustus.

The late Emperor had been at Mambij (Herapolis) on the Euphrates preparing for the march against Iulianus.
From Antioch he begun his journey when he passed the headless corpse of a man lying on the road, he took this as an omen.
When he got to Tarsus he came down with a fever, he tried to continue before he had to stop at the town of Mopsucrenae where he took to his sick bed.

On November 3rd 361AD he died at the age of forty-four, he had never had a serious illness before and it is likely he was poisoned by Pagan sympathisers.

Iulianus was careful to hide his feelings upon hearing this 'news' at Naisus.

The new Augustus went to the Capital to attend the funeral at the Holy Apostles church.
He made a great show of mourning and ordered the whole city to follow suit, he waited on the quayside to be there for the arrival of the coffin.

Iulianus led the funeral procession to the church, weeping false tears along the way.
It was the last time he ever took part in a church service.
Once it was over he began to delve into the attributes of an Emperor.