Hamas terrorists are resuming their presence in northern Gaza Strip, months after the IDF had initially cleared the Strip except for the far south of the Strip: Rafah and a couple small villages near Rafah.
[R]enewed violence, in areas Israeli forces had previously largely cleared of Hamas, serves as a sobering example for Israel’s forces of the difficulty of consolidating gains as they prepare an offensive in Rafah, the militant group’s last major bastion.
It’s certainly true that clearing an area of the remnants of a terrorist entity that operates as a dispersed network and that is skilled at (literal) underground operations and keeping that area clear is deucedly difficult.