, ▁he ▁was ▁a ▁native ▁of ▁T usc any . ▁By ▁ 4 3 1 , ▁as ▁a ▁de acon , ▁he ▁was ▁sufficiently ▁well ▁known ▁outside ▁of ▁Rome ▁that ▁John ▁Cass ian ▁dedicated ▁to ▁him ▁the ▁treat ise ▁against ▁N est or ius ▁written ▁at ▁Leo ' s ▁suggestion . ▁About ▁this ▁time ▁Cy ril ▁of ▁Alexand ria ▁appe aled ▁to ▁Rome ▁regarding ▁a ▁juris dict ional ▁dispute ▁with ▁Ju ven al ▁of ▁Jerusalem , ▁but ▁it ▁is ▁not ▁entirely ▁clear ▁whether ▁the ▁letter ▁was ▁intended ▁for ▁Leo , ▁in ▁his ▁capacity ▁of ▁arch de acon , ▁or ▁for ▁Pope ▁Cel est ine ▁I ▁directly . ▁Near ▁the ▁end ▁of ▁the ▁reign ▁of ▁Pope ▁Si xt us ▁III , ▁Leo ▁was ▁dispatch ed ▁at ▁the ▁request ▁of ▁Emperor ▁Val entin ian ▁III ▁to ▁sett le ▁a ▁dispute ▁between ▁A ë ti us , ▁one ▁of ▁Ga ul ' s ▁chief ▁military ▁command ers , ▁and ▁the ▁chief ▁magistr ate ▁Ca ec ina ▁De cius ▁Ag in ati us ▁Al bin us . ▁Johann ▁Peter ▁Kir sch ▁sees ▁this ▁commission ▁as ▁a ▁proof ▁of ▁the ▁confidence ▁placed ▁in ▁the ▁able ▁de acon ▁by ▁the ▁Imperial ▁Court . ▁ ▁Pap acy ▁During ▁his ▁absence ▁in ▁Ga ul , ▁Pope ▁Si xt us ▁III ▁died ▁( 1 1 ▁August ▁ 4 4 0 ), ▁and ▁on ▁ 2 9 ▁September ▁Leo ▁was ▁un anim ously ▁elected ▁by ▁the ▁people ▁to ▁succeed ▁him . ▁ ▁So on ▁after ▁assuming ▁the ▁pap al ▁throne ▁Leo ▁learned ▁that