crusade

cru·sade
kro͞oˈsād/Submit
noun
1.
a medieval military expedition, one of a series made by Europeans to recover the Holy Land from the Muslims in the 11th, 12th, and 13th centuries.
verb
1.
lead or take part in an energetic and organized campaign concerning a social, political, or religious issue.
"he crusaded against gambling in the 1950s"
synonyms: campaign, fight, do battle, battle, take up arms, work, strive, struggle, agitate, lobby, champion, promote
"she likes crusading for the cause of the underdog"