1 9 3 6 ▁to ▁ 1 9 4 0 . ▁ ▁He ▁was ▁Att orney ▁General ▁of ▁Mont ana ▁from ▁ 1 9 4 1 ▁to ▁ 1 9 4 2 . ▁ ▁He ▁res igned ▁as ▁Att orney ▁General ▁to ▁join ▁the ▁U . S . ▁Army ▁as ▁a ▁Major , ▁during ▁World ▁War ▁II . ▁He ▁was ▁promoted ▁to ▁the ▁rank ▁of ▁colon el , ▁and ▁received ▁several ▁med als ▁for ▁courage ous ▁service . ▁ ▁After ▁he ▁returned ▁from ▁the ▁War , ▁he ▁ran ▁for ▁Governor ▁of ▁Mont ana ▁in ▁ 1 9 4 8 , ▁winning ▁the ▁Democratic ▁primary ▁and ▁adv ancing ▁to ▁the ▁general ▁election , ▁where ▁he ▁defeated ▁inc umb ent ▁Republican ▁Governor ▁Sam ▁C . ▁Ford ▁by ▁a ▁wide ▁margin . ▁Bon ner ▁ran ▁for ▁re - e lection ▁in ▁ 1 9 5 2 , ▁and ▁he ▁was ▁narrow ly ▁defeated ▁by ▁State ▁Senator ▁J . ▁Hugo ▁Ar ons on . ▁He ▁ran ▁for ▁Governor ▁again ▁in ▁ 1 9 5 6 , ▁but ▁lost ▁the ▁Democratic ▁primary ▁to ▁Arnold ▁O ls en , ▁who ▁ended ▁up ▁losing ▁to ▁Ar ons on ▁in ▁the ▁general ▁election . ▁In ▁ 1 9 6 0 , ▁when ▁United ▁States ▁Senator ▁James ▁E . ▁Murray ▁opt ed ▁not ▁to ▁run ▁for ▁re - e lection , ▁Bon ner ▁ran ▁to ▁succeed ▁him , ▁but , ▁in ▁a ▁crow ded ▁primary , ▁was ▁defeated ▁by ▁Congress man ▁Lee ▁Met cal f , ▁who ▁would ▁go ▁on ▁to ▁serve