Declarations of victory over ISIS by both Iraq and Syria, along with Russia, are not having an impact on US military policy in the region, according to Defense Secretary James Mattis, who insisted on Friday that "the war is not over."

Which isn't to say that the US is determined to keep fighting a war against ISIS, as such, but rather that there's definitely going to be a war against somebody in those countries. Mattis in particular has been keen to talk up the idea of an "ISIS 2.0" emerging in areas ISIS has been expelled from.

Mattis' comments are very interesting in the context of other Pentagon statements, which have insisted that US troops would stay in Iraq and Syria long after the ISIS war has ended. This had long been assumed to be just a quiet, permanent garrisoning of the two countries, particularly controversial in Syria since they don't welcome a US military presence.

Instead, Mattis seems to be presenting this as not just an open-ended deployment, but an open-ended war against an ever-changing collection of enemies.