Eve of Destruction
2001Magneto launches a final assault on Genosha, establishing a mutant nation by force. With most of the X-Men captured, Jean Grey hastily assembles a ragtag team of volunteers — including former villains and civilians — for a desperate rescue mission. The last traditional X-Men story before Grant Morrison's revolutionary New X-Men relaunch rewrites the rules.
4 core issues, 0 optional tie-ins/crossovers

The Uncanny X-Men #392
Jean Grey assembles an impromptu rescue team; Magneto holds the X-Men captive in Genosha

X-Men #112
The rescue team infiltrates Genosha

The Uncanny X-Men #393
Jean's team fights through Magneto's forces

X-Men #113
Magneto is defeated; the pre-Morrison era ends; the X-Men enter a new chapter