J Gresham Machen was the most influential leader of fundamentalism during the modernist-fundamentalist controversy of the 1920's and 1930's. His background, training, and life's work as a New Testament scholar (and author) at Princeton Theological Seminary are chronicled, but his primary influence is shown to be as a staunch defender of the truth against the attacks of the modernists who compromised biblical faith and practice. Yet Dr Machen's gracious manner is exhibited even in his break with Princeton and the Presbyterian Church as he founded Westminster Theological Seminary and the Orthodox Presbyterian Church.