expression, godan verb (-su)
violate the border; invade the frontier
Fixed expression meaning to illegally cross or encroach upon a national border. Often used in political or military contexts.
武装集団が国境を侵した。
An armed group violated the border.
隣国の軍隊が国境を侵す恐れ
There is a risk that the neighboring country's military will invade the frontier.