Andreatta was throughout his career a promoter of a mixed economic system and between the pupils of his main school of thought the most important was Romano Prodi, which he sponsored as a guide for the center-left coalition after the fall of the first Berlusconi government in 1995.
Prodi nominated him as defense minister in his first government (May 1996 - October 1998 ), where Andreatta made a number of significant proposals: the reform of the General Staff, the 'abolition of conscription, the reform of the civil service.