[This is a work-in-progress and is subject to change.]
Although Treize fully intended to die in the war of A.C. 195, he made preparations for the possibility, however slim, that his plans might fail and he might survive.
He was found in time to be saved, though just barely. He was brought to a private medical institution, where his presence was not questioned, and was kept quiet [note: this part may sound a bit iffy, but I am still working on it]. He spent more than a year and a half there—a little over a year in a coma, and several months after in recovery.
Currently, he is living alone, aside from a few house staff members, and is staying out of the public eye, keeping a low profile as much as possible in the hopes of not disturbing the newly-won peace. Only a few trusted individuals know of his survival. He has changed somewhat since the war, but still retains the same ideals.