He made significant academic contributions to fields of American labor unions and anti-Communism.

[6] His mother was Herta Marcus (1901–1981) from the East Prussian town of Gilgenburg (now Dąbrówno, Poland).

Although they had planned to leave Germany for Palestine, instead they emigrated to America in 1943, where they changed the surname from Liebeskind to Leab.

[1][6][9] Provost John Duff appointed him to oversee the university's American Studies Program.

He served as acting chairman of the Department of History and two years as chair of University Rank and Tenure Committee.

[2][9] He wrote or edited seven books, published more than 90 articles, and lectured extensively in Europe and America.

[2][9][11] He was a senior Fulbright lecturer at the University of Cologne two times (1977 spring, 1986–1987) and in 2008 he was a visiting professor of history there.

[11] In the 1960s, Leab served as an editorial assistant of and contributing editor to the Columbia Journalism Review.

[4][5][6] Colleague David Culbert praised Leab's book Orwell Subverted as "masterly.