Fukuyama's "End of History" thesis never claimed wars would literally stop. It argued that, after the Cold War, liberal democracy + market economies had become the final form of human government, no viable ideological alternative remained that could seriously challenge it on a civilisational scale. The big contests over how humans should organise power and economy were, in that view, settled.
What we actually got was something messier: the ideological contest cooled, but the material contests (territory, resources, status, security dilemmas, identity, great-power rivalry) did not. So, history kept producing wars, just not the kind that used to decide between communism and capitalism, or monarchy and republic. We got frozen conflicts, proxy wars, civil wars that never quite end, and now the return of higher-intensity state-on-state fighting.
"Forever war" is less a new invention than the re-emergence of the default human pattern once the temporary post-1945 and post-1989 restraints weakened. Great-power competition, weak states, demographic pressures, resource stress, and the diffusion of cheap destructive technology all push in the same direction. Liberal institutions and norms still exist and still constrain some actors, but they never abolished the underlying drivers.
War is a recurring feature of the human condition rather than a temporary aberration. Fukuyama was describing the exhaustion of ideological alternatives, not the end of conflict itself. The latter was always a category error. History didn't end; it just changed the kind of history it was writing.
https://www.foreignaffairs.com/united-states/new-forever-wars