As in: “Black World War II and Korean War veterans represented the vanguard of grassroots civil rights leadership in the war against white supremacy and social oppression during the 1950s and 1960s” (Cox, 2013, p.74).
Cox, M. S. (2013). Segregated soldiers: Military training at historically black colleges in the Jim Crow South. Retrieved from http://ebookcentral.proquest.com.library.emmanuel.edu:2048/lib/emmanuel/reader.action?ppg=74&docID=1092476&tm=1503165756340
For definitions of vanguard, consult the Oxford English Dictionary.