the vanguard

剑桥词典

the part of an army or navy that leads an attack on an enemy
先頭部隊，先鋒；尖兵
比較
rearguard

a group of people who lead the development of new ideas , or a leading position in the development of something
（思想的）先敺；領先地位
He is in the vanguard of economic reform . 他是經濟改革的領頭人。
也見
the forefront 返回 the vanguard