Used for literal battle lines, as well as the leading edge of a movement, technology, or trend.
彼は最前線で戦った。
He fought on the front line.
この研究所は医療技術の最前線にいる。
This research institute is at the forefront of medical technology.
He stood at the front line of the war.
She is active at the forefront of AI development.
The new recruits were sent to the front line.
The unit withdrew from the front line.