Vermont’s Norwich University says it has received a $25 million gift, the school’s largest ever, ahead of its bicentennial fund-raising campaign. The private military college announced the gift on Friday. The gift is from the Tawani Foundation, an organization with a mission of enhancing the awareness and understanding of the importance of the citizen soldier. Foundation President J.N. Pritzker said it gives him ‘‘great joy’’ to support Norwich’s upcoming fund-raising campaign to ensure Norwich has the facilities and resources to meet every challenge. Norwich President Richard Schneider said the gift will transform the university.