 He officially retired in 1985, but remained active as an emeritus professor.Tutte was instrumental in helping to found the Department of Combinatorics and Optimization at the University of Waterloo.His mathematical career concentrated on combinatorics, especially graph theory, which he is credited as having helped create in its modern form, and matroid theory, to which he made profound contributions; one colleague described him as "the leading mathematician in combinatorics for three decades".