front line; forefront
最前線の医師から生の声が届いた。
Firsthand accounts came from doctors on the front line.
彼は技術革新の最前線を歩んできた。
He has been walking at the forefront of technological innovation.
最前線に立つ兵士は常に命の危険と隣り合わせだ。
Soldiers on the front line are always one step away from death.