VANGUARD

[noun] [U] [formal] - the front part of a group of people who are moving forward esp. an army, or (figurative) who are making changes or developmentsA UN peace-keeping vanguard arrived in the area this week.The families who arrived this week were only the vanguard of what turned into a flood of refugees.(figurative) He sees himself as being in the vanguard of economic reform.See also forefront. Compare rearguard.