vanguard

noun
1
the leaders of a movement in society, for example in politics, art, industry, etc.
پیشگامان, طلیعه‌, پیشرو, طلایه‌دار, پیشگام, جلودار
2
the part of an army, etc. that is at the front when moving forward to attack the enemy
طلایه, پیشقراول, صف مقدم, نیروی پیشرو
The army was advancing steadily and the vanguard was already at the border.
opposite rearguard